Work around win 8.1 sdk aapi.h problem

qgroundcontrol.pro

@@ -185,7 +185,8 @@ WindowsBuild {
 	QMAKE_CXXFLAGS_WARN_ON += /W3 \
         /wd4996 \   # silence warnings about deprecated strcpy and whatnot
         /wd4005 \   # silence warnings about macro redefinition
-        /wd4290     # ignore exception specifications
+        /wd4290 \   # ignore exception specifications
+        /Zc:strictStrings-  # work around win 8.1 sdk sapi.h problem
     WarningsAsErrorsOn {
         QMAKE_CXXFLAGS_WARN_ON += /WX
     }