showbc: Quote block name, so it was easily visible.
py, unix: Add -v option, print bytecode dump if used.

This will work if MICROPY_DEBUG_PRINTERS is defined, which is only for
unix/windows ports. This makes it convenient to user uPy normally, but
easily get bytecode dump on the spot if needed, without constant recompiles
back and forth.

TODO: Add more useful debug output, adjust verbosity level on which
specifically bytecode dump happens.
py-version.sh: Make it work in case no git tag is present.
tests: Add framework for comparative benchmarking.

Motivation is optimizing handling of various constructs as well as
understanding which constructs are more efficient in MicroPython.
More info: http://forum.micropython.org/viewtopic.php?f=3&t=77

Results are wildly unexpected. For example, "optimization" of range
iteration into while loop makes it twice as slow. Generally, the more
bytecodes, the slower the code.
tests/bench/var: Add tests for class/instance var access.

Also compared with method abstraction for accessing instance vars -
it's more than 3 times slower than accessing var directly.