Either not needed anymore, or defined in the board/_hal_conf.h file.

Tweaked a couple of the USB files to compile if neither dev nor host was defined.
Tested on netduiono plus 2 and stm32f4discovery boards

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

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).

Some functionality is still missing (eg and, or, bit shift), and some
things are buggy (eg subtract).

This commit also introduces board directories and moves board
specific config into the appropriate board directory.

boards/stm32f4xx-af.csv was extracted from the STM32F4xx datasheet
and hand-tweaked.

make-pins.py takes boards/stm32f4xx-af.csv, boards/stm32f4xx-prefix.c,
and boards/BOARD-NAME/pins.csv as input and generates the file
build/pins_BOARD_NAME.c

The generated pin file for PYBOARD4 looks like this:
https://gist.github.com/dhylands/9063231

The generated pins file includes all of the supported alternate
functions, and includes upsupported alternate functions as comments.

See the commnet block at the top of stm/pin_map.c for details on
how to use the pin mapper.

I also went ahead and modified stm/gpio.c to use the pin mapper.

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

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.

This also fixes up the IRQ for the PYBOARD4 USERSW
although I was unable to test that functionality.

* Add MICROPY_HW_HAS_LCD
* Add MICROPY_HW_HAS_WLAN
* Use feature test macros in main

* Add some generic feature macros to mpconfigport
* Move pin and port definitions from usrsw.c to mpconfigport

mpconfigport.h is now included by stm32f4xx.h so that all STM files have
access to these defines.

mpconfig.h will automatically pull mpconfigport.h.

A big change.  Micro Python objects are allocated as individual structs
with the first element being a pointer to the type information (which
is itself an object).  This scheme follows CPython.  Much more flexible,
not necessarily slower, uses same heap memory, and can allocate objects
statically.

Also change name prefix, from py_ to mp_ (mp for Micro Python).