Added LoadText() function

Actually, renamed ReadTextFile() from rlgl and make it public

src/raylib.h

@@ -925,6 +925,7 @@ RLAPI RayHitInfo GetCollisionRayGround(Ray ray, float groundHeight);
 // Shaders System Functions (Module: rlgl)
 // NOTE: This functions are useless when using OpenGL 1.1
 //------------------------------------------------------------------------------------
+RLAPI char *LoadText(const char *fileName);                               // Load chars array from text file
 RLAPI Shader LoadShader(char *vsFileName, char *fsFileName);              // Load shader from files and bind default locations
 RLAPI void UnloadShader(Shader shader);                                   // Unload shader from GPU memory (VRAM)