mescc: Support mini-mes running scheme program with builtins.

mescc: Support mini-mes running scheme program with builtins.

Mini-mes, compiled with either gcc or mescc, now runs a memory dump of
this mini-0.mes program

	(begin
	  (write-byte (make-cell 0 0 65))
	  (write-byte (make-cell 0 0 66))
          (write-byte (make-cell 0 0 67))
 	  (write-byte (make-cell 0 0 10))
	  #f)

when read and dumped by (gcc-compiled) mes-32.

* build-aux/mes-snarf.scm: FIXES ..collapse?
* module/language/c99/compiler.mes (ast->info): Bail out on unhandled
  declarations.  Was: verbosely skip.