Add autogen.sh

We want ./configure to be an auto-generated file.  Now, instead of
running `./configure`, you run `./autogen.sh && ./configure`.
Add a `make TIMED=1` option

Copied from coq_makefile.

Also, make some paths hopefully a bit more robust to building in a
different directory.
Add an `html` target

Mostly copied from coq_makefile.  I'm not sure if I got the links into
the standard library correct.
Run `autoreconf -vi`

I have automake 1.11.1, not 1.13.1.  And since I'll be modifying
configure.ac and Makefile.in, I want to collect all the churn into a
single place.

I'd be much happier just depnding on autoconf, and not including these
files.
Update configure.ac

Hopefully this will improve portability.  We now quote more things, ask
to check for more programs, replace a useless "test -n" with a
meaningful "test -x", use "AC_MSG_CHECKING" more, and be more compatible
with silly users who set COQBIN to ! and have a "test" that interprets
`test -n "!"` wrong, and be more compatible with crufty users who have
a "test" which barfs on 'test "" = "no"'.
autoreconf -vi
Update Makefile.am

Use $(MKDIR_P), $(LN_S), and be more uniform about $(srcdir) and
$(srccoqdir).

This closes #184.
autoreconf -vi
Merge pull request #188 from JasonGross/fixup-autoconf

Fixup autoconf. The churn is irrelevant, you will survive as an expert user. The mathematician in the street who already has a hard time compiling coq and learning git will curse you for requiring autoconf tools. And we will curse you if you bundle things in .tar.gz, thereby teaching people not to use git ;-)
Merge branch 'make-html' of https://github.com/JasonGross/HoTT into JasonGross-make-html

Conflicts:
	Makefile.am
	Makefile.in
	configure

I put back in the files generated by autoconf to make ordinary people's
lives easier. I hope Jason can live with "the churn".