Ignore C4091 warnings caused by inclusion of DbgHelp.h on Windows

There's a bug in this header file provided by the Win SDK,
so just disable this warning for any QGIS source files which include
DbgHelp.h

src/app/CMakeLists.txt

@@ -480,6 +480,15 @@ IF(PEDANTIC)
   ENDIF(MSVC)
 ENDIF(PEDANTIC)
 
+IF(MSVC)
+# -wd4091 Avoid 'typedef' ignored on left of '' when no variable is declared warning in DbgHelp.h
+SET_SOURCE_FILES_PROPERTIES(
+  qgisapp.cpp
+  main.cpp
+  qgscrashhandler.cpp
+  PROPERTIES COMPILE_FLAGS -wd4091)
+ENDIF(MSVC)
+
 INCLUDE_DIRECTORIES(
   ${CMAKE_SOURCE_DIR}/src/app
   ${CMAKE_SOURCE_DIR}/src/app/composer

src/core/CMakeLists.txt

@@ -540,6 +540,10 @@ ELSE(NOT MSVC)
     pal/feature.cpp
     pal/pointset.cpp
     PROPERTIES COMPILE_FLAGS -wd4702)
+  # -wd4091 Avoid 'typedef' ignored on left of '' when no variable is declared warning in DbgHelp.h
+  SET_SOURCE_FILES_PROPERTIES(
+    qgsstacktrace.cpp
+    PROPERTIES COMPILE_FLAGS -wd4091)
 ENDIF(NOT MSVC)
 
 SET(QGIS_CORE_MOC_HDRS