Fix DEBUG=1 builds

Without this fix, I get the following error:

CC gccollect.c
gccollect.c: In function ‘gc_helper_get_regs’:
gccollect.c:63:1: error: bp cannot be used in asm here
windows: Complete rename of MICROPY_PATH_MAX to MICROPY_ALLOC_PATH_MAX (58ebde4)
Merge pull request #629 from dhylands/fix-unix-debug

Fix unix DEBUG=1 builds
Merge pull request #631 from stinos/fix-win-def

windows: Complete rename of MICROPY_PATH_MAX to MICROPY_ALLOC_PATH_MAX (...
Revert "Fix DEBUG=1 builds"

This reverts commit 6e76f7bc90fcd130db888f8804b8555dc8f3a484.

This patch tries to workaround a previous clang workaround. Instead of going
into workaround of workaround spiral, the original workaround should be tamed.
tests: Add argument to allow specifying which directories to test
unix/gccollect.c: Make Clang workaround apply only to it. Unbreaks gcc builds.
py: Implement long int parsing in int(...).

Addresses issue #627.
py: Make int(<longint>) work by just returning the longint.
py: Fix check of small-int overflow when parsing ints.

Also unifies use of SMALL_INT_FITS macro across parser and runtime.
msvc: Only update generated headers when there are changes

This fixes generating the headers casuing complete rebuilds,
even when the headere's content didn't really change.
py: Implement bignum '&' with negatives on lhs and rhs.

Needs proper coverage testing.  Doesn't implement -ve & -ve.
Addresses issue #611.
qemu-arm: Add port README.

Based on https://github.com/micropython/micropython/pull/630 by @errordeveloper.
Merge pull request #633 from stinos/msvc-fix-genhdr-dep

msvc: Only update generated headers when there are changes
objstr: *strip(): Fix handling of one-char subject strings.
objstr: *strip(): If nothing is stripped, don't create dup string.
py: Fix break from within a for loop.

Needed to pop the iterator object when breaking out of a for loop.  Need
also to be careful to unwind exception handler before popping iterator.

Addresses issue #635.
tests: Add test for break in for.

For #635 / 25c84643b6c4da169cdb11de54f027e3c477c301.
modsocket: Remove stale ifdef.
modsocket: Add some comments on intended usage/API design of module.