Conditional compilation is not handled correctly

[TheMostDiligent]

Compiling the following shader:

#version 430 core

void main()
{
#if 0
#   define MACROS(S) #S
#endif
}

fails with the following error :

ERROR: 0:6: '#' : (#) can be preceded in its line only by spaces or horizontal tabs 
ERROR: 0:7: '' : missing #endif 
ERROR: 0:7: '' : compilation terminated 
ERROR: 3 compilation errors.  No code generated.

This is a regression that was introduced by feb5437