Issue #290. This currently fails, to draw attention to the issue.

OS X compatible -map syntax for LDFLAGS

Allow ports to define statically builtin functions.

Implement "from mod import *"

Done by introducing another factored out helper API in binary.c. This API
can be reused also by array and struct modules.

Convert unix open() to such.

unix Makefile: Split off optimization options to COPT variable.

To allow easily try different optimization and configuration options
without patching any files.

Some tools do not support local/static symbols (one example is GNU ld map file).
Exposing all functions will allow to do detailed size comparisons, etc.

Also, added bunch of statics where they were missing, and replaced few identity
functions with global mp_identity().

For some reason, STM port, while it's 32 bit, needs %lu and %ld for
printing machine_uint_t and machine_int_t.

Enable GC for Unix port

Enable link map file generation.

Bah - Removed a couple of warnings for teensy that I didn't notice before.

Note: none of these functions are used by STM port, so they're provided
to have parity with pre gc refactor status quo, and in case they will be
needed in the future by some extension writers.

With range(10000), doesn't fit into 128K heap.

Please don't submit patches with tab indentation!

Test function needs to be called by something else. Test heap size reduced so
its dump fits on a screenful of a typical terminal.