[IMGUI] Bitwise OR of flags can result in an invalid type cast back to flag enum type
### Current behavior
In order to apply multiple flags to something (i.e. `igInputTextWithHint()`), you first need to get the ordinal values of all the flag enums (`ord()`), chain all the flags you want into an expression using the bitwise `or` operator, then type cast the resulting integer back into the enum type. For example:
```nim
(
  ord(ImGuiWindowFlags.NoResize) or
  ord(ImGuiWindowFlags.NoCollapse) or
  ord(ImGuiWindowFlags.NoMove) or
  ord(ImGuiWindowFlags.NoBringToFrontOnFocus)
).ImGuiWindowFlags
```
Normally this works fine (except for [warning you about holey enums](https://github.com/nimgl/nimgl/issues/69)), but certain combinations of flags can result in an integer that is greater than the maximum value allowed by the enum type. For example:
```nim
(
  ord(ImGuiInputTextFlags.CharsDecimal) or
  ord(ImGuiInputTextFlags.CallbackEdit)
).ImGuiInputTextFlags
```
In this example, this expression will evaluate to 524289. However, Nim will not allow the type conversion to `ImGuiInputTextFlags` to work due to the fact that the maximum ordinal value declared in the `ImGuiInputTextFlags` type is 524288, one less than the result of this expression. This code will not compile as a result, even though in theory it should be valid.

### Steps and minimal example
To create this error, simply combine any set of flags that would result in a value greater than the maximum value of a given enum's type. [Minimal example](https://gist.github.com/Knaque/636c94ab0abf384878cadbacbf5dd208).

### Expected behavior
Procedures with flags should accept any combination of flags.

### Environment

  - Version: 1.3.2
  - OS: MacOS
  - Bindings: ImGui
  - Backend: C++
  - Nim Version: 1.6.0
  - Compiler used: GCC

### Suggested fix
Replace the procedure argument's type with `int`/`uint`. This will also remove the holey enums warning. The caveat with this fix is that it will no longer be obvious what the available flags are, but this can be remedied by instead using doc comments to tell the programmer what flag type they should be referencing.
