[m-dev.] for review: remove Prolog support

[Zoltan Somogyi]

> compiler/options.m:
> compiler/handle_options.m:
> compiler/globals.m:
> 	Delete code for handling the options `--generate-prolog',
> 	`--prolog-dialect', and `--heap-space' (which was used
> 	for NU-Prolog only).

The change to delete --generate-prolog and --prolog-dialect should be undone.
They are not for executing Mercury programs directly with Prolog; they are
(or will be) for translating Mercury programs, including those using functions
etc, to Prolog. This may not be complete, but there removing it would be
counter-productive.

You also missed something that should be deleted: the code to build a SICStus
version of stage2 in tools/bootcheck.

Zoltan.