Prepare for VS2015

Prepare for VS2015
https://bugs.webkit.org/show_bug.cgi?id=146579

Reviewed by Jon Honeycutt.

Source/JavaScriptCore:

* heap/Heap.h:
Fix compiler error by explicitly casting zombifiedBits to the size of a pointer.

Source/WebCore:

* WebCore.vcxproj/build-generated-files.pl:
Find a correct preprocessor when using VS2015.

Source/WTF:

* wtf/StdLibExtras.h:
(std::exchange):
Added preprocessor macros around functions implemented in VS2015's standard library.

Tools:

* WinLauncher/stdafx.h:
Define __STDC_LIMIT_MACROS to have access to INTMAX_MAX.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@187702 268f45cc-cd09-0410-ab3c-d52691b4dbfc