Merge the 'safe' parts of my StrnCpy patch - many of the users really wanted

Merge the 'safe' parts of my StrnCpy patch - many of the users really wanted
a pstrcpy/fstrcpy or at most a safe_strcpy().

These have the advantage of being compiler-verifiable.

Get these out of the way, along with a rewrite of 'get_short_archi' in the
spoolss client and server.  (This pushes around const string pointers, rather
than copied strings).

Andrew Bartlett
(This used to be commit 32fb801ddc035e8971e9911ed4b6e51892e9d1cc)