Correct the known-good commit value

The STABLE variable in the Makefile and the generation tooling pointed
to the commit after the one which was the latest known-good point. This
commit points them back to the appropriate commit, with the right
version number.
Merge pull request #1 from gracelang/version-skew

Changes the STABLE commit value back to 2104
Fixes bug in indexOf when needle not found.

Also fixes same bug in lastIndexOf.
Enlarges tests for string methods.

Now includes tests for indexOf.  Also adds collectionsPrelude
to GRACE_MODULES so that node.js test harness can find them.
Merge branch 'master' into dupDecls.

Brings this branch up to date with fixes on master.
Merge branch 'master' into dupDecls.

Merges independent fixes from master.