wx.nim produces illegal C++ code

[Fredrik Høisæther Rasch]

When compiling wx.nim the nim compiler produces illegal C++ code, probably because the nim bindings are incorrect in respect to the contents of the wxWidgets header files.

Examplary output from the VCC compiler backend: (generated by running: nim cpp examples/purewx/example1)

.\examples\purewx\nimcache\wxnim_wx.cpp(126): error C2440: '=': cannot convert from 'const char *' to 'NCSTRING'
.\examples\purewx\nimcache\wxnim_wx.cpp(126): note: Conversion loses qualifiers