Cleaned up make variables for compilers and linker to consistently use CXX for C++ compiler, CC for C compiler and LD for linker.
Reviewed-by: dholmes, ohrstrom
Changed the conditional to see if the precompiled header has been specified. Also, removed the unused PrecompiledOption.
Reviewed-by: dholmes, brutisso
Added an ifndef DONT_USE_PRECOMPILED_HEADER to precompiled.hpp. Set up DONT_USE_PRECOMPILED_HEADER when compiling with Sun Studio or when the user specifies USE_PRECOMPILED_HEADER=0. Fixed broken include dependencies.
Reviewed-by: coleenp, kvn
