Jeremy merged across my string parinoia fixes, but forgot to enable them! :-)

Jeremy merged across my string parinoia fixes, but forgot to enable them! :-)

This patch catches up on the rest of the work - as much string checking
as is possible is done at compile time, and the rest at runtime.

Lots of code converted to pstrcpy() etc, and other code reworked to correctly
call sizeof().

Andrew Bartlett
(This used to be commit c5b604e2ee67d74241ae2fa07ae904647d35a2be)