constructors: Unify C:, CONSTRUCTOR:, NAMED-CONSTRUCTOR:, and DEFAULT-CONSTRUCTOR: by requiring the class name after the constructor word name.

example: CONSTRUCTOR: <foo> foo ( stack effect -- obj ) ;

The benefit is that we can now search for <foo> by name and it's not auto-generated--less magic. Also, there are fewer kinds of constructors.

Rename CONSTRUCTOR-SYNTAX: to SLOT-CONSTRUCTOR: since it's more descriptive.
extra: Update usages of CONSTRUCTOR: for new parameter.
Link to the Python binding documentation from the Python vocabulary
forestdb: Support more api calls.
gtk.ffi: Find the right gtk library in a startup-hook. Necessary because gtk is not in the same place on varius distros, so just find it on demand. Fixes #1185.
Revert "gtk.ffi: Find the right gtk library in a startup-hook. Necessary because gtk is not in the same place on varius distros, so just find it on demand. Fixes #1185."

This reverts commit 0ef942e400951bdce9924446f621bf4c0049fc40.
Remove executable bit from tons of files that aren't
forestdb: Support snapshots and rollbacks, change how with-forestdb works. Unit test things.
forestdb.ffi: Make fdb_iterator_opt_t its own type and remove comment.
forestdb.lib: Implement iterators and some related stuff.
Document possible bugs for now.
forestdb.lib-tests: Test iterators.
forestdb: Add iteration by seq-num. Add tests for iteration by seq-num.
Document potential bugs.
forestdb.lib: Relax our expectations of ALIEN: slots and save other slots to doc tuple.
forestdb.lib: fdb_doc has to be malloc'd. Iterators have to fdb_doc_free docs. Add with-doc and with-create-doc combinators. Unit testing fdb-get etc.
forestdb.lib: iterator needs to call free on docs.
forestdb.lib: Must close with WAL commit or else data gets lost on next open.
forestdb: Update for new api changes. Fix some unit tests, they look better now.
forestdb.ffi: Fix up api.
compiler.tests.alien: Check in a failing unit test. Structure is getting returned improperly.
vm: Oops, test doesn't take a long long.
cpu.x86.64: 64-bit register is RDX not EDX. Fixes #1191.
assocs: Add zip-index, zip-index-as and docs/tests.
sequences: Add map-index-as for symmetry and docs/tests.