Initial cut at writing COERCE-TO-COMPILED-PROCEDURE in Scheme. The

Initial cut at writing COERCE-TO-COMPILED-PROCEDURE in Scheme.  The
next change will be to make the compiler generate calls to this
procedure rather than the primitive COERCE-TO-COMPILED-PROCEDURE,
which should result in both faster generation and invocation of
trampolines.

Eventually we might make the linker use this code too.

The code is a bit hairy and needs special initialization, hence the
changes in make.scm.