[MLton] Intel Mac version of MLton

[Stephen Weeks]

> It appears that some documentation is not getting generated:
...
> mv: rename /Users/jhr/Work/mlton/mlton/install/usr/local/share/doc/ 
> mlton/guide/mlton-guide.pdf to /Users/jhr/Work/mlton/mlton/install/ 
> usr/local/share/doc/mlton/mlton-guide.pdf: No such file or directory
...
> Yeah, I see the same problem on x86-linux, so obviously the
> Makefiles need some tweaking.

The "docs" target of the main Makefile calls bin/make-pdf-guide to
make doc/guide/mlton-guide, but only if "htmldoc" can be run.  The
install-docs target is what John and Matthew are seeing fail.  The
offending line is

	mv $(TDOC)/guide/mlton-guide.pdf $(TDOC)/

which fails presumably because mlton-guide.pdf doesn't exist.  So,
"make install-no-docs" should indeed work.  Other possibilities are to
install htmldoc, build mlton.pdf on another machine, or to grab it
from another package.


As to fixing the Makefile, I'm not sure if anything should be changed.
We could tweak the offending line to

	if [ -r $(TDOC)/guide/mlton-guide.pdf ]; then \
		mv $(TDOC)/guide/mlton-guide.pdf $(TDOC)/; \
	fi

But I'm not sure silently dropping the PDF MLton guide is better than
reporting the error and requiring one of the above workarounds.