jsoncpp: Disable warnings to avoid changing 3rd party code

Add '-w' or equivalent flag on compilers supporting it.
Tell MSVC to use its lowest warning level inside jsoncpp sources.

Utilities/cmjsoncpp/CMakeLists.txt

@@ -1,5 +1,13 @@
 project(JsonCpp CXX)
 
+# Disable warnings to avoid changing 3rd party code.
+if(CMAKE_CXX_COMPILER_ID MATCHES
+    "^(GNU|Clang|AppleClang|XL|VisualAge|SunPro|MIPSpro|HP|Intel)$")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -w")
+elseif(CMAKE_CXX_COMPILER_ID STREQUAL "PathScale")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -woffall")
+endif()
+
 set(JSONCPP_SOURCES
   src/lib_json/json_batchallocator.h
   src/lib_json/json_reader.cpp

Utilities/cmjsoncpp/include/json/config.h

@@ -9,6 +9,10 @@
 // Include KWSys Large File Support configuration.
 #include <cmsys/Configure.h>
 
+#if defined(_MSC_VER)
+# pragma warning(push,1)
+#endif
+
 /// If defined, indicates that json library is embedded in CppTL library.
 //# define JSON_IN_CPPTL 1