Remove -Werror

--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -174,7 +174,6 @@ include(Dependencies)
 
 # Set compiler specific build flags
 if (CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang" OR CMAKE_CXX_COMPILER_ID MATCHES "Intel")
-	add_compile_options(-Werror)
 	if (NOT MYGUI_HIGH_LEVEL_WARNINGS)
 		add_compile_options(-w)
 	else ()