MICROPY_ENABLE_FLOAT is automatically set in mpconfig.h if MICROPY_FLOAT_IMPL
is set to a non-zero value.

Fix makeqstrdata.py to work in Python 2.7

mp_module_obj_t can now be put in ROM.

Configuration of float type is now similar to longint: can now choose
none, float or double as the implementation.

math module has basic math functions.  For STM port, these are not yet
implemented (they are just stub functions).

Fix gc_realloc to expand in place

* Issue #322

unix: Allow to set heap size using "-X heapsize=N" option.

Addresses issue #327.

Checks for non-default args following default args, and errors out.
Addresses issue #328.

Implement collections.namedtuple

I.e. as replacement of MP_OBJ_IS_TYPE(), which takes into account subclassing.

Implement machine_sqrt using VSQRT

Support building "unix" port for ARM

Implement not, shl and shr in mpz library.  Add function to create mpzs
on the stack, used for memory efficiency when rhs is a small int.
Factor out code to parse base-prefix of number into a dedicated function.