PrecompiledHeader.h: Removed WTF-redefines

Removed redefinition of TRUE and FALSE, and removed typedef of int to BOOL
Revert "PrecompiledHeader.h: Removed WTF-redefines"

This reverts commit 9fdb3187767ae3589a98e126175f885c9b8391e6.
Added comment explaining redefinition of BOOL
Merge pull request #197 from archshift/no-comprende

PrecompiledHeader.h: Add a comment to clarify redefinition of BOOL