benchmark.reverse-complement.tests,mason.report.tests: fix for the test
cases so they write to temp files instead of in resource:
mason.report: dos2unix.
furnace.db: db-persistence needs a dispose word that delegates to its pool slot

tests in http.tests refactored using "with-words" so that they always
dispose any db-persistence instances they create.
VM: try and recover with a kernel error from the callback heap running out
VM: "formalize" the callback_heaps object allocation using a
bump_allocator<code_block>

The advantage of doing it this way is that you can reuse the existing
each_object method to iterate all callbacks
VM: use a free_list_allocator for the callbacks, that way they can
individually be freed
VM: new primitive (callback-room) for querying the VM about memory usage

The word works exactly like (code-room) except it looks at the memory
usage in the callback heap instead of the code heap.
stack-checker.known-words: stack effect for <callback> is switched, it
should be ( word integer -- alien )
VM: new primitive free-callback which is able to free a callback
previously allocated using <callback>
alien: a test and docs for free-callback
stack-checker.alien: use free-callback as a destructor when creating
callbacks

+ tests proving it works. now in case you create temporary callbacks you
can enclose them in with-destructors and it will just work(tm).
alien,stack-checker.alien: move callback-destructor to the alien vocab

It can't be placed in stack-checker.alien because that vocab isn't
included in deployed images which lead to weird errors when the
destructors trigger.
compiler.tests.alien: wrap all callback tests in special
unit-test-with-destructor blocks, that way they dont leak memory in the
callback heap
db.postgresql: configurable test db setting

adds a \ postgresql-db global (analoguous to the \ imap-settings one)
which holds settings to a postgres db so that the tests have something
to test against.
db.tester: the postgresql-db variable shouldn't be mutated
db.postgresql: ensure that 2 line error messages are handled
prettyprint.backend: use , not % in unparse-ch.
build-support: test failed on mac somehow, add a timeout so it fails faster.
python.throwing: new module to support capturing python tracebacks
python: tests and plug a reference leak in the exception throwing code