WiP addition of support for ValveFS to many more filesystem  natives.
Improved FPrint(f) passthrough
More progress:
Abstracted many fs funcs with helper class.
Removed much duplicated code.
Fixed ReadFile assuming FS errors for ValveFS.
Added ValveFS support for ReadFileString, WriteFile, WriteFileString, DeleteFile.
Added missing param in doc for OpenFile.
Add more accurate return value for DeleteFile when using Valve FS.
Add ValveFS support to more filesystem functions: OpenDirectory (CloseHandle on directory) ReadDirEntry DirExists CreateDirectory RenameFile
Fix compile error on with MSVC.
Fix backwards use_valve_fs logic for OpenDirectory
Add missing use_valve_fs param to CreateDirectory native def
Add support for specifying gameinfo search path when using valveFS in file natives
Fix syntax errors in files.inc
Fix another syntax error in files.inc
Clarify return value commit on RemoveFile
Merge pull request #120 from alliedmodders/wip-valve-fs2

Add support for Valve FS to natives that use file handles (r=asherkin).