Pointers are 2x bigger on 64 bit machines, so we should allocate twice
the memory to have a comparable heap size.

Str modulo

In addition to memory allocation failure, other problem was that 10**17
was overflowing.  Now passes.

Previous overflow test was inadequate.

A malloc/realloc fail now throws MemoryError.

Works on x86.

The alternate form for floating point doesn't work yet.
The %(name)s form doesn't work yet.

Home/end work in picocom and screen (different codes in those 2
programs).  Also, CTRL-A (for non-empty liny) and CTRL-E act as
home/end.

stmhal: Reimplement file support using stream protocol API.

To run the tests on the pyboard you need to set the "test_on_pyboard"
variable to "True", and also have tools/pyboard.py available for import
(easiest is to symlink to it).

Retested again on Ubuntu 12.04 armhf running in chroot on Samsung
ARM Chromebook (Cortex-A15).

This adds readline(), readall(), etc. methods. Also other fixes to make
Python API compliant and "with" support.

So far just includes "open" function, which should be supplied by a port.

TODO: Make the module #ifdef'ed.

unix: Enable GC.

Conflicts:
	py/objstr.c

Also fix objstr.c to compile when floats disabled.

Also change formating modifier in test script (it still passes with
original format though).

GC support for "unix" port was implemented some time ago, but still not
enabled.

Fail currently.

For example, we still build w/o GC enabled, so cannot really set heap size.

Previosuly just silently exited.