lm4f: Update makefile for "make flash" support

When the makefile was originally written, openocd did not officially
support ICDI. Now that ICDI support is part of an official openocd release,
update the makefile to enable flashing with "make flash".
Updated locm3 submodule.
Updated libopencm3.
lm4f: Update examples to the new GPIO API

We updated the GPIO API to use the AHB bus; however the AHP aperture for
GPIO ports A through J needs to be explicitly enabled at runtime. Accessing
the AHB aperture otherwise hardfaults.

To make the examples work again, we call gpio_enable_ahb_aperture() at the
start of main().

Since we're at it, we also take out the ugly register accesses in favor
of the new gpio functions.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Updated to the new locm3 changed to stdint types.
lm4f: Add USB to serial (CDCACM) example

Implements a USB-to-serial adapter, compliant to the CDCACM subclass.
UART1 is used for the TX/RX lines. Although UART1 also has lines for flow
control, they are not used. Instead, the control lines are implemented in
software via GPIOA.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
lm4f: Add USB bulk device example

I wrote this example to benchmark the USB driver. See the README.md for
full details.

Why README.md instead of just README. README.md shows up better on github,
and makes it easier to browse the tree on github to search for an example.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Switched sewly added files to stdint types, as the pull request was done before the switch.
Added missing _write prototype.
OLIMEX STM32-H107 has a 25MHz crystal
Changed echo usage for printf as it is more portable.
Updated libopencm3. Disabled lpc43xx examples.

We merged a huge patchset for lpc43xx that breaks the examples. As we
are waiting for those to be updated it is better to disable the
automatic build of them.
stm32f3discovery examples added.

- miniblink
- button
- fancyblink
- adc
- Non tested yet! But they compile.
stm32f3discovery ld script corrected as recommended in #82.
Flashing now using openocd. GDB Debugging possible and tested :).
Adc example fixed (printing garbage before) and cleaned.

- Integer printing function fixed.
  	  - because of comparison against smaller than 0 numbers we must use signed numbers!
	  - Value zero was not printed at all.
	  - It was printing one more character than it should.
- Erasing unnecesary commentaries.
- Erasing debugging help.
stm32f3discovery: Adding i2c accelerometer example.
stm32f3discovery: Moving read and write convinience functions to libopencm3.
stm32f3discovery: spi l3gd20 example added.
stm32f3: cdcacm example added and tested.