Codechange: Remove duplicated includes. (#10888)

These are now included by stdafx.h so don't need to be included again.

Codechange: rename str_validate to StrMakeValid(InPlace) (#9304)

This to be more explicit the function changes the value, and not
returns yes/no.

Fix: Globally apply preprocessor directive coding style

Global; except for the 32-bit SSE blitter, which has some #DEFINEs
in not-very-nice places.

Codechange: Replace custom thread code with C++11 thread objects.

We assume a conforming C++11 compiler environment that has a valid <thread>-header.
Failure to run a real thread is handled gracefully.