Avoid creating the hash in an object when it isn't needed.

svn path=/trunk/tools/build/v2/; revision=83834
Try to fix path handling for the Jam executable.

svn path=/trunk/tools/build/v2/; revision=83836
Avoid reprocessing toolset.requirements.

svn path=/trunk/tools/build/v2/; revision=83846
Optimize property-set.create-from-user-input.

svn path=/trunk/tools/build/v2/; revision=83847