Applied patches from Mattias Ellert  (ROOT-6506) concerning unknown options on old gcc compilers.
Applied patch from Ben Morgan (ROOT-6512 - RootConfiguration.cmake hardcodes paths into installed ROOTConfig.cmake)
Implement CTestCustom.cmake files in sources. Attempt to fix ROOT-6529
Remove last static from zip/inc/Bits.h
Add missing error flag initialization and setting
Remove unused #define
introduce RZip.h with ROOT-specific functions, do not expose other includes from core/zip/inc
Use RZib.h in ROOT instead of direct functions declarations

Conflicts:
	core/zip/CMakeLists.txt
add RZip.cxx into cmake file

Conflicts:
	core/zip/CMakeLists.txt
Move 'private' headers to src directory