Remove "system.h" from headers

Inclusion of "system.h" in headers results to significant overhead, especially on win32 (forces include of "windows.h", "dx9.h"...)
In this PR platform configuration part was moved to new header "PlatformConfig.h".
Include of basic definition headers was added to linux/PlatformDefs.h and win32/PlatformDefs.h. Now win32/PlatformDefs.h has definition for DWORD, HANDLE... similar to linux/PlatformDefs.h (no need for "windows.h" just for win32 types)
Includes of "system.h" in headers was mostly removed or replaced with "PlatformConfig.h" and "PlatformDefs.h"
All files with "HAS_xx" was manually inspected. Possibly fixed few places with missing include of configuration (missing defs of "HAS_xx").