Add "vsyasm", a batch version of yasm primarily useful for VS2010.

Add "vsyasm", a batch version of yasm primarily useful for VS2010.

Basically the objfile, listfile, and mapfile options specify output
directories instead of files.  Multiple files are accepted and each one
is independently assembled in command line order.  All options (such
as include directories and predefined macros) apply to all input files.
Any error terminates the process early.

Suggested by: Brian Gladman

svn path=/trunk/yasm/; revision=2284