Fix ^= operator in shaders

servers/visual/shader_language.cpp

@@ -445,6 +445,10 @@ ShaderLanguage::Token ShaderLanguage::_get_token() {
 			case ':':
 				return _make_token(TK_COLON);
 			case '^':
+				if (GETCHAR(0) == '=') {
+					char_idx++;
+					return _make_token(TK_OP_ASSIGN_BIT_XOR);
+				}
 				return _make_token(TK_OP_BIT_XOR);
 			case '~':
 				return _make_token(TK_OP_BIT_INVERT);