The function and corresponding command-line option are only enabled for
the coverage build.  They are used to exercise uPy features that can't
be properly tested by Python scripts.

The 2 removed from coverage build are: -Wredundant-decls and
-Wstrict-prototypes.

To address issue #699.

GC for unix/windows builds doesn't make use of the bss section anymore,
so we do not need the (sometimes complicated) build features and code related to it

Confirmed that it improves perfomance of simple "for i in range(N): pass"
loop by 15% on Core2.

This build is primarily intended for benchmarking, and may have random
features enabled/disabled to get high scores in synthetic benchmarks.
The intent is to show/prove that MicroPython codebase can compete with
CPython, when configured appropriately. But the main MicroPython aim
still remains to optimize for memory usage (which inevitibly leads to
performance degradation in some areas on some workloads).

Add more specific comments describing what is going on.

Force OSX to compile with clang even if gcc is available
Change LDFLAGS syntax to be compatible with clang
Fix questionable syntax on line 90
Remove extraneous tab character

For the sake of older versions of gcc (and other compilers), don't use
the #warning CPP directive, nor the -Wno-error=cpp option.

Also, fix a strict alias warning in modffi.c for older compilers, and
add a test for ffi module.

Addresses issue #847.

And move the MAP_ANON redefinition from py/asmx64.c to unix/alloc.c.

Fixes issue #840

Also add -t/--target option to pip-micropython to allowing installing to
the pyboard.

Thanks to turbinenreiter/Sebastian Plamauer for the patch.

Also provides setraw() function from "tty" module (which in CPython is
implemented in Python). The idea here is that 95% of "termios" module usage
is to set raw mode to allow access to normal serial devices. Then, instead
of exporting gazillion termios symbols, it's better to implement it in C,
and export minimal number of symbols (mostly baud rates and drain values).

The idea is that it should be possible to pass any additional params for
experimentation without need to patch sources (and without need to deviate
from or repeat baseline options).

Some people want to enable even more warnings. Let them do it without putting
burden on everyone. Some people vice versa think that current settings should
be relaxed. In this regard, -Werror is the most problematic, it disallows to
use #warning directive, and disallows to pass configuration settings on make
command lines. Again, until decided how to deal with these globally, allow to
work around these problems locally.

  there are special tweaks and paths to be considered. Just provide some
  defaults, in case the values are undefined.
- py-version.sh does not need any bash specific features.
- Use libdl only on Linux for now. FreeBSD provides dl*() calls from libc.

This reverts commit 6e76f7bc.

This patch tries to workaround a previous clang workaround. Instead of going
into workaround of workaround spiral, the original workaround should be tamed.

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

Now of the form MICROPY_PY_*.  See issue #35.

stat() is bad function to use using FFI, because its ABI is largely private.
To start with, Glibc .so doesn't even have "stat" symbol. Then, layout of
struct stat is too implementation-dependent. So, introduce _os to deal
with stat() and other similar cases.

It's a hack, but can't find a cleaner way to do it.

Any generated headers go in $(BUILD)/genhdr/, and are #included as
'genhdr/xxx.h'.

As discussed in #504