TST: weave tests: clean up ast/blitz/catalog tests.

Basic changes - no docstrings, imports, run_module_suite
TST: weave tests: clean up build_tools/c_spec/ext_tools tests.
TST: weave tests: clean up tests for numpy_scalar/size_check/inline_tools
TST: weave tests: clean up weave_test_utils and slice_handler tests.

Also remove duplicate remove_whitespace function in a number of files.
TST: weave tests: clean up scxx_* tests and make scxx_timings run again.
TST: weave tests: silence a large amount of test noise.  Add BlitzWarning.
TST: weave tests: remove more test noise, fix use of global temp dirs.
TST: weave tests: don't leave .so/cpp files in dir from which tests are run.
TST: weave tests: add context manager to create/clean tempdirs for blitz().

Closes gh-2092.
BUG: put back dbhash import in weave/catalog.py, while unused it had a purpose

Issue without this import observed by Warren with Anaconda on gh-3182.
See comments in commit for more details.
TST: avoid use of unsafe mktemp and cleanup test_dir in test_c_spec
MAINT: weave: A few tweaks:

* Remove an unused function ('test_function()') from blitz_tools.py
* Fix a typo in a comment in test_blitz_tools.py
* Remove a commented-out line of code from test_ext_tools.py
Merge pull request #3182 from rgommers/weave-tests

Make weave tests behave