Make pyboard.enter_raw_repl more robust

In case there's a program in the microcontroller's main.py running in an infinite loop
More relaxed parsing of preprocessed qstr header

The original parsing would error out on any C declarations that are not typedefs
or extern variables. This limits what can go in mpconfig.h and mpconfigport.h,
as they are included in qstr.h. For instance even a function declaration would be
rejected and including system headers is a complete no-go.
That seems too limiting for a global config header, so makeqstrdata now
ignores everything that does not match a qstr definition.
Merge pull request #543 from lurch/patch-4

Make pyboard.enter_raw_repl more robust
stmhal: Remove #include <stdint.h> from mpconfigport.h.

Make include dependencies neater, and adheres to the coding convention
that headers should not include headers.
Merge pull request #546 from stinos/relax-makeqstrdata

More relaxed parsing of preprocessed qstr header