[Win] Implement memoryFootprint for Windows

[Win] Implement memoryFootprint for Windows
https://bugs.webkit.org/show_bug.cgi?id=171693

Reviewed by Alex Christensen.

This patch implements memoryFootprint for Windows. In Windows, we calculate the size
of private working set. This can be done by enumerating private pages in working set.

And we also split MemoryFootprint.cpp to cocoa, linux, and win versions.

* WTF.xcodeproj/project.pbxproj:
* wtf/CMakeLists.txt:
* wtf/MallocPtr.h:
(WTF::MallocPtr::operator*):
(WTF::MallocPtr::operator->):
* wtf/PlatformGTK.cmake:
* wtf/PlatformJSCOnly.cmake:
* wtf/PlatformMac.cmake:
* wtf/PlatformWin.cmake:
* wtf/cocoa/MemoryFootprintCocoa.cpp: Copied from Source/WTF/wtf/MemoryFootprint.cpp.
(WTF::memoryFootprint):
* wtf/linux/MemoryFootprintLinux.cpp: Renamed from Source/WTF/wtf/MemoryFootprint.cpp.
(WTF::forEachLine):
(WTF::memoryFootprint):
* wtf/win/MemoryFootprintWin.cpp: Added.
(WTF::memoryFootprint):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@216731 268f45cc-cd09-0410-ab3c-d52691b4dbfc