Improve release process

[fare]

• [x] Get the build scripts to work perfectly with and without git present, including the handling of version.
• [x] In particular, correctly handle the Gambit version in absence of git — generate src/gambit/include/stamp.h from manifest.
• [x] The source tarball autogenerated by GitHub does not include the Gambit module. Fix that or work around it somehow?
• [ ] Automate the production of binary tarballs, rpm and debian packages.
• [x] A binary tarball for Linux depends on .so's that may or may not be present. Have a tarball or dependencies handy? (Heroku notably does not provide the sqlite.so that we need)

[fare]

It is probably too late to automate away these issues for v0.18.1, but hopefully we can get it all push-button or v0.18.2.

[ober]

yes we can.

[iacore]

Is there a way to build gerbil without gambit, since it is self-bootstrapped?

[vyzo]

no, we are very deeply integrated with gambit.

In principle you could bootstrap from another scheme however.