Fix compilation errors on Windows
 In case of a 2D scatter plot drawing (with or without option COL) the automatically
computed lower limits of the histogram's axis might be 0. In that case it is better to set them
to the minimum of the data set (if it is >0) to avoid data cut when plotting in log scale.
Added protection to not use __thread for MacOSX  <= 10.7 and gcc
Implement CTestCustom.cmake files in sources. Attempt to fix ROOT-6529.
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
Correct handling of rootrc Unix.*.Root.UseThreads

InitThreads requires the interpreter to be initalized.

Also extend it to actually initialize the TThread mechanism (it was previously
just loading the library and creating the TClass object for TThread).

This fixes ROOT-6379
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
introduce RZip.h with ROOT-specific functions, do not expose other includes from core/zip/inc
add RZip.cxx into cmake file
Move 'private' headers to src directory
Fix CMake broken by previous commit
Make parameters/options from LLVM/CLANG as advanced (hide them from GUIs). Avoid rebuilding after a 'cmake'.
White space
Replace the global in ZTrees.h by thread local state (initialiation is costly)
When using the builtin zlib we need to public some of the headers.

For example TPDF.cxx on Windows uses zlib.h
Avoid shadow variable/struct name