changes include:
* use single GPIO.BSRR instead of BSRRH and BSRRL
* change HSE_STARTUP_TIMEOUT to 100 ms
* define LSE_STARTUP_TIMEOUT to 5 s

This needs to land afte #1407 lands, since #1407 is where
the CMSIS_MCU was defined.

To build:

make BOARD=ESPRUINO_PICO

To deploy: short the BOOT0/BTN contact on the back of the board (eg by
drawing over it with a graphite pencil), then hold down BTN while
inserting the board into the USB port.  The board should then enter DFU
mode, and the firmware can be downloaded using:

make BOARD=ESPRUINO_PICO deploy

This config option is for the USB OTG pin, pin A10.  This is used on
some boards but not others.  Eg PYBv3 uses PA10 for LED(2), so it
shouldn't be used for OTG ID (actually PA10 is multiplexed on this
board, but defaults to LED(2)).

Partially addresses issue #1059.

This patch updates ST's HAL to the latest version, V1.3.0, dated 19 June
2014.  Files were copied verbatim from the ST package.  Only change was
to suppress compiler warning of unused variables in 4 places.

A lot of the changes from ST are cosmetic: comments and white space.
Some small code changes here and there, and addition of F411 header.

Main code change is how SysTick interrupt is set: it now has a
configuration variable to set the priority, so we no longer need to work
around this (originall in system_stm32f4xx.c).

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

Enumerates CDC device over USB, but doesn't transmit/receive yet.

This compiles and links, but hasn't been tested on a board
yet and even if it was run, it doesn't currently do anything.