+ xBRZ high quality image scaling

http://www.vogons.org/viewtopic.php?f=41&t=34125
http://sourceforge.net/projects/hqmame/files/xBRZ.zip
Note: this implementation requires C++11 so it’s unusable without modifications
* modify xBRZ to suit GZDoom project

+ build with C++98 compiler: static asserts are disabled, preprocessor macro is used instead of lambda
+ basic support for alpha channel
* replace degree symbol in comments
* enable hqNx everywhere
+ xBRZ to high quality texture resize modes