Fixed compiler warning with new OpenGL ES header files

src/render/opengles2/SDL_gles2funcs.h

@@ -53,7 +53,7 @@ SDL_PROC(void, glPixelStorei, (GLenum, GLint))
 SDL_PROC(void, glReadPixels, (GLint, GLint, GLsizei, GLsizei, GLenum, GLenum, GLvoid*))
 SDL_PROC(void, glScissor, (GLint, GLint, GLsizei, GLsizei))
 SDL_PROC(void, glShaderBinary, (GLsizei, const GLuint *, GLenum, const void *, GLsizei))
-SDL_PROC(void, glShaderSource, (GLuint, GLsizei, const char **, const GLint *))
+SDL_PROC(void, glShaderSource, (GLuint, GLsizei, const GLchar* const*, const GLint *))
 SDL_PROC(void, glTexImage2D, (GLenum, GLint, GLint, GLsizei, GLsizei, GLint, GLenum, GLenum, const void *))
 SDL_PROC(void, glTexParameteri, (GLenum, GLenum, GLint))
 SDL_PROC(void, glTexSubImage2D, (GLenum, GLint, GLint, GLint, GLsizei, GLsizei, GLenum, GLenum, const GLvoid *))