Add cache coders
https://bugs.webkit.org/show_bug.cgi?id=138413

Reviewed by Anders Carlsson.

Add encoding and decoding support for cache types.

This is largely a copy of the IPC coder classes with some unnecessary features removed.
The coders compute a type-sensitive checksum that can be used to verify the data integrity.

The code is behind ENABLE(NETWORK_CACHE) and not yet used.

* NetworkProcess/cache: Added.
* NetworkProcess/cache/NetworkCacheCoder.h: Added.
* NetworkProcess/cache/NetworkCacheCoders.cpp: Added.
* NetworkProcess/cache/NetworkCacheCoders.h: Added.
* NetworkProcess/cache/NetworkCacheDecoder.cpp: Added.
* NetworkProcess/cache/NetworkCacheDecoder.h: Added.
* NetworkProcess/cache/NetworkCacheEncoder.cpp: Added.
* NetworkProcess/cache/NetworkCacheEncoder.h: Added.
* WebKit2.xcodeproj/project.pbxproj:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@175748 268f45cc-cd09-0410-ab3c-d52691b4dbfc