Various updates for/around Guppy.

Some fairly wide-ranging changes to the front-end (changed langparser_t
structure a bit to cater for language-specific libraries), some more file-
handling bits.  The cccsp back-end is now able to put generated Guppy code
through the C compiler (determined from KRoC) automatically.  Not extensively
tested.
Various back-end updates for cccsp.
Fixed (mostly) stack allocation for Guppy/cccsp.

The cccsp back-end now calls gcc to get stack usage information, then
feeds this back in the reallocate pass and re-generates the code.
Also pushed top-level handling inside, such that the top-level PAR is
constructed rather than dropped verbatim.
Added standard-library header for Guppy.
Various Guppy updates.

Now seems to be doing mostly the right thing with stack frame allocation.
Far from the efficiency of occam-pi compiled code, but certainly reasonable
enough for most applications.  Note: memcpy is a stack hungry resource..
Couple of small updates to Guppy test program.