This is in preparation for supporting other MCU series, such as
STM32F2xx.  Directory structure for the HAL is now hal/f4/{inc,src},
where "f4" will in the future be different for other series.

HAL source/header files that are not use are removed to reduce the size
of the code.

SysTick IRQ now increases millisecond counter directly (ie without
calling HAL_IncTick).  Provide our own version of HAL_Delay that does a
wfi while waiting.  This more than halves power consumption when running
a loop containing a pyb.delay call.  It used to be like this, but new
version of HAL library regressed this feature.

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).

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.