Fix Emscripten build.

src/renderer_gl.h

@@ -87,6 +87,7 @@ typedef double GLdouble;
 typedef int64_t  GLint64;
 typedef uint64_t GLuint64;
 #		define GL_PROGRAM_BINARY_LENGTH GL_PROGRAM_BINARY_LENGTH_OES
+#		define GL_NUM_PROGRAM_BINARY_FORMATS GL_NUM_PROGRAM_BINARY_FORMATS_OES
 #		define GL_HALF_FLOAT GL_HALF_FLOAT_OES
 #		define GL_RGBA8 GL_RGBA8_OES
 #		define GL_UNSIGNED_INT_2_10_10_10_REV GL_UNSIGNED_INT_2_10_10_10_REV_EXT