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

Added definitions for SPI1, SPI2, and SPI3
Removed USB stuff (that could be removed)
Updated BOARD name defintion

This makes the board match the name printed on the board (and
agree with the documentation)

Includes full version of pins.csv file with correct mapping of the Nucleo
STM32F401RE chip (LQFP64 package).

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

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).

All board config macros now begin with MICROPY_HW_.

Renamed PYBv10 to PYBV10, since macros should be all uppercase.

Made SDCARD_DETECT configurable in mpconfigport.h, so that the SD
detect pin can be easily configured.

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.