proc be overrided when apply onSymbol proc in cPlugin
I wrap the GDAL library with nimterop, the generated code is as follows:
```
proc OGR_G_GetGeometryRef*(a1: OGRGeometryH, a2: cint): OGRGeometryH {.impgdalC.}
proc OGR_F_GetGeometryRef*(a1: OGRFeatureH): OGRGeometryH {.impgdalC.}
```
when applide onSymbol proc in cPlugin:
```
cPlugin:
  import strutils

  proc lowercaseAscii(s: string): string =
    if s.len == 0: result = ""
    else: result = toLowerAscii(s[0]) & substr(s, 1)

  proc onSymbol*(sym: var Symbol) {.exportc, dynlib.} =
    sym.name = sym.name.strip(chars = {'_'})

    if sym.kind == nskProc:
      if sym.name.contains("OGR_G_"):
        sym.name = sym.name.replace("OGR_G_").lowercaseAscii
      elif sym.name.contains("OGR_F_"):
        sym.name = sym.name.replace("OGR_F_").lowercaseAscii
```
the generated code with only one line as follows:
```
proc getGeometryRef*(a1: OGRGeometryH, a2: cint): OGRGeometryH {.impgdalC.}
```
the same name proc with different parameters:
```
proc getGeometryRef*(a1: OGRFeatureH): OGRGeometryH {.impgdalC.}
```
it  is overrided, something must be wrong?