The goal of this fix is that developers and pushbuild should do
(roughly) the same when compiling the source code.
- same set of compiler switches
- same set of features built
- same set of tests enabled/executed


To this end, mysql_release.cmake has been split in three:
compiler_options.cmake 
  standardized compiler flags
  -O has been removed from Debug build
  (developers don't want anything optimized away when debugging)
feature_set.cmake      
  standardized feature set built is "community"
mysql_release.cmake    
  things needed by pushbuild, in particular DEBUG_EXTNAME

Most of the scripts in BUILD have been removed.
Exceptions are
compile-dist         still used by PB
compile-pentium-gcov still used by PB

Some compile-pentium-xxx have been re-written, and
are left as examples of how to configure cmake for gprof/valgrind debug/optimized.