Use -Os rather than -O2 as our compilation flag, document why.
Document why we always use gcc over clang.
Fix openssl path in gambit.
Stop trying to make static openssl.
Using a yet unreleased development version of gambit,
so as to be able to build a recent gerbil.
Update the way gambit is bootstrapped, which involves building a
release version of gambit (which for a development gambit, is not the
same version as the current version of gambit).