Put the GASNet source files back how they were. I'm going to apply the
official GASNet version of the changes to those files instead.
Remove arbitrary limit on command line length

This commit is a minor variation on one contributed by Greg Titus
of Cray.  The purpose is to remove the arbitrary 1024-character
limit on the length of the ssh command line run via system() when
AMUDP is using SPAWNFN=S.  This allows for a much longer command
line, as required by the Chapel runtime when using this spawner.