Enabled "warnings as errors" on MSVC and set warning level to /W3 explicitly.

Reaching /W4 requires further work.

globals.cmake

@@ -55,7 +55,7 @@ elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
 		-Wno-missing-braces)
 
 elseif(MSVC)
-	set(MIRRAGE_DEFAULT_COMPILER_ARGS /DWIN32_LEAN_AND_MEAN /DNOMINMAX /MP)
+	set(MIRRAGE_DEFAULT_COMPILER_ARGS /DWIN32_LEAN_AND_MEAN /DNOMINMAX /MP /W3 /WX)
 	set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} /ignore:4221")
 	set(CMAKE_STATIC_LINKER_FLAGS "${CMAKE_STATIC_LINKER_FLAGS} /ignore:4221")
 endif()