Fixed C++ compilation in C literal in call to SetShapesTexture

[codecat]

This fixes the same problem mentioned in #33, but I guess this particular line was introduced later.

I see there's RAYGUI_CLITERAL but also CLITERAL from raylib, is there a reason for this distinction?

[raysan5]

@codecat thanks for the review!

The distinction us because, despite raygui depends a lot on raylib, other backends could be added (RAYGUI_STANDALONE) and raylib could be not included...