Issue in nnp_maxpooling.nim only when using `koch temp c`
I noticed a weird discrepancy between running 

    nim c examples/ex02_handwritten_digits_recognition.nim

vs 
    
    koch temp c /home/fabian/github/Arraymancer/examples/ex02_handwritten_digits_recognition.nim

(having just re-compiled nim itself, i.e., they should behave identically.)

ex02_handwritten_digits_recognition compiles fine when using release mode nim, but compilation fails with the debugging compiler. The offensive line is [this](https://github.com/mratsim/Arraymancer/blob/249218eb64476c5aec34ca15d0dcf0955fbb418c/src/nn_primitives/nnp_maxpooling.nim#L55). Replacing `-Inf.int` by `low(int)` seems to solve the problem, but I'm not sure if this works the same.

Traceback:

```
/home/fabian/github/Arraymancer/src/nn_primitives/nnp_maxpooling.nim(55, 24) Error: over- or underflow
Traceback (most recent call last)
nim.nim(113)             nim
nim.nim(77)              handleCmdLine
main.nim(173)            mainCommand
main.nim(77)             commandCompileToC
modules.nim(137)         compileProject
modules.nim(77)          compileModule
passes.nim(236)          processModule
passes.nim(125)          processTopLevelStmt
sem.nim(577)             myProcess
sem.nim(545)             semStmtAndGenerateGenerics
semstmts.nim(1864)       semStmt
semexprs.nim(803)        semExprNoType
semexprs.nim(2311)       semExpr
semexprs.nim(787)        semDirectOp
semexprs.nim(683)        afterCallActions
sem.nim(444)             semMacroExpr
sem.nim(396)             semAfterMacroCall
semexprs.nim(2424)       semExpr
semstmts.nim(1805)       semStmtList
semexprs.nim(2442)       semExpr
semstmts.nim(1661)       semProc
semstmts.nim(1590)       semProcAux
semexprs.nim(1488)       semProcBody
semexprs.nim(2424)       semExpr
semstmts.nim(1805)       semStmtList
semexprs.nim(2424)       semExpr
semstmts.nim(1805)       semStmtList
semexprs.nim(2282)       semExpr
semexprs.nim(1217)       semFieldAccess
semexprs.nim(1086)       builtinFieldAccess
semexprs.nim(44)         semExprWithType
(22 calls omitted) ...
semexprs.nim(1086)       builtinFieldAccess
semexprs.nim(44)         semExprWithType
semexprs.nim(2285)       semExpr
semexprs.nim(2316)       semExpr
semexprs.nim(787)        semDirectOp
semexprs.nim(684)        afterCallActions
semexprs.nim(19)         semTemplateExpr
sem.nim(418)             semAfterMacroCall
semexprs.nim(2424)       semExpr
semstmts.nim(1805)       semStmtList
semexprs.nim(2344)       semExpr
semexprs.nim(710)        semIndirectOp
semexprs.nim(2342)       semExpr
semexprs.nim(786)        semDirectOp
semexprs.nim(639)        semOverloadedCallAnalyseEffects
semcall.nim(441)         semOverloadedCall
semcall.nim(403)         semResolvedCall
seminst.nim(347)         generateInstance
seminst.nim(146)         instantiateBody
semexprs.nim(1488)       semProcBody
semexprs.nim(2424)       semExpr
semstmts.nim(1805)       semStmtList
semexprs.nim(2426)       semExpr
semstmts.nim(455)        semVarOrLet
semtypes.nim(1355)       semTypeNode
semtypes.nim(1453)       semTypeNode
semtypes.nim(1193)       semGeneric
seminst.nim(217)         instGenericContainer
semtypinst.nim(124)      replaceTypeVarsT
semtypinst.nim(452)      replaceTypeVarsTAux
semtypinst.nim(379)      handleGenericInvocation
sigmatch.nim(2377)       instTypeBoundOp
seminst.nim(347)         generateInstance
seminst.nim(146)         instantiateBody
semexprs.nim(1488)       semProcBody
semexprs.nim(2424)       semExpr
semstmts.nim(1805)       semStmtList
semexprs.nim(2422)       semExpr
semexprs.nim(1418)       semAsgn
semstmts.nim(1864)       semStmt
semexprs.nim(803)        semExprNoType
semexprs.nim(2424)       semExpr
semstmts.nim(1805)       semStmtList
semexprs.nim(2427)       semExpr
semstmts.nim(460)        semVarOrLet
semexprs.nim(44)         semExprWithType
semexprs.nim(2330)       semExpr
semexprs.nim(786)        semDirectOp
semexprs.nim(639)        semOverloadedCallAnalyseEffects
semcall.nim(441)         semOverloadedCall
semcall.nim(403)         semResolvedCall
seminst.nim(347)         generateInstance
seminst.nim(146)         instantiateBody
semexprs.nim(1488)       semProcBody
semexprs.nim(2424)       semExpr
semstmts.nim(1805)       semStmtList
semexprs.nim(2434)       semExpr
semstmts.nim(703)        semFor
semstmts.nim(635)        semForVars
semstmts.nim(1864)       semStmt
semexprs.nim(803)        semExprNoType
semexprs.nim(2424)       semExpr
semstmts.nim(1805)       semStmtList
semexprs.nim(2434)       semExpr
semstmts.nim(721)        semFor
semstmts.nim(635)        semForVars
semstmts.nim(1864)       semStmt
semexprs.nim(803)        semExprNoType
semexprs.nim(2424)       semExpr
semstmts.nim(1805)       semStmtList
semexprs.nim(2434)       semExpr
semstmts.nim(721)        semFor
semstmts.nim(635)        semForVars
semstmts.nim(1864)       semStmt
semexprs.nim(803)        semExprNoType
semexprs.nim(2424)       semExpr
semstmts.nim(1805)       semStmtList
semexprs.nim(2434)       semExpr
semstmts.nim(721)        semFor
semstmts.nim(635)        semForVars
semstmts.nim(1864)       semStmt
semexprs.nim(803)        semExprNoType
semexprs.nim(2424)       semExpr
semstmts.nim(1805)       semStmtList
semexprs.nim(2426)       semExpr
semstmts.nim(460)        semVarOrLet
semexprs.nim(44)         semExprWithType
semexprs.nim(2342)       semExpr
semexprs.nim(787)        semDirectOp
semexprs.nim(695)        afterCallActions
semexprs.nim(570)        evalAtCompileTime
semfold.nim(649)         getConstExpr
msgs.nim(1074)           localError
msgs.nim(1059)           liMessage
msgs.nim(913)            handleError
msgs.nim(898)            quit
FAILURE
```