fixed sRGB-texture related compile erros for gles 2.0

src/renderer_gl.h

@@ -337,6 +337,30 @@ typedef uint64_t GLuint64;
 #	define GL_COMPRESSED_RGB_BPTC_UNSIGNED_FLOAT_ARB 0x8E8F
 #endif // GL_COMPRESSED_RGB_BPTC_UNSIGNED_FLOAT_ARB
 
+#ifndef GL_SRGB8_ALPHA8
+#define GL_SRGB8_ALPHA8 0x8C43
+#endif // GL_SRGB8_ALPHA8
+
+#ifndef GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT 0x8C4D
+#endif // GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT
+
+#ifndef GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT 0x8C4E
+#endif // GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT
+
+#ifndef GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT
+#define GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT 0x8C4F
+#endif // GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT
+
+#ifndef GL_COMPRESSED_SRGB8_ETC2
+#define GL_COMPRESSED_SRGB8_ETC2 0x9275
+#endif // GL_COMPRESSED_SRGB8_ETC2
+
+#ifndef GL_COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2
+#define GL_COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2 0x9277
+#endif // GL_COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2
+
 #ifndef GL_TRANSLATED_SHADER_SOURCE_LENGTH_ANGLE
 #	define GL_TRANSLATED_SHADER_SOURCE_LENGTH_ANGLE 0x93A0
 #endif // GL_TRANSLATED_SHADER_SOURCE_LENGTH_ANGLE