ENH: Adding kwsys::SystemTools::FileTimeCompare method to compare file modification times with the highest resolution possible on the file system.

ENH: Added try-compile KWSYS_STAT_HAS_ST_MTIM.  This tests whether struct stat has the extra st_mtim member that has high resolution times.

ENH: Added try-compile KWSYS_STAT_HAS_ST_MTIM.  This tests whether struct stat has the extra st_mtim member that has high resolution times.

ENH: Removing collapsing of files to full path before checking.  The current working directory is set correctly because the dependency lines are used by make anyway.  This drastically improves the speed of dependency checking.

ENH: Avoid generating duplicate rules for an object file.  A warning about duplicate source files in a target is now generated.

BUG: Removing "guess when there is a space in the path" check for chdir command.  It is the responsibility of the caller of the command to ensure the arguments are properly quoted on the command line.