Addresses issue #558, but it's likely that other out-of-memory errors
could crash the pyboard. Reason is that qstrs use m_new and can raise
an exception within the parser.
Blanket wide to all .c and .h files. Some files originating from ST are
difficult to deal with (license wise) so it was left out of those.
Also merged modpyb.h, modos.h, modstm.h and modtime.h in stmhal/.