Add a script for code coverage testing using the "coverage" module.

(script was taken from https://bitbucket.org/optiflowsrd/obelus/ )
Fix a crash due to invalid IR generation for STORE_MAP

(the variables weren't fetched through Interpreter.get() and therefore were suppressed by the unused temps removal phase)
Merge pull request #606 from pitrou/test_coverage2

Add a script for code coverage testing using the "coverage" module.
Merge pull request #609 from pitrou/store_map_crash

Fix a crash due to invalid IR generation for STORE_MAP
Merge branch 'master' of github.com:numba/numba into refleak_testing