L4 and F3 actually have the same bits to write in the same order, but F3 hides
the name of the deep power down bit. Keep the like that for now, but there's a
standard API for enabling and disabling the regulator.
Just the basic core common functionality gained for free by being a common
peripheral. Enough for a miniblink.
Fixes some errors in the GPIO memory map. ST's naming of AHB2 vs AHB3 is
confusing.
Values from RM0351rev1, with the correction of the duplicate TIM1_CC entry.
Only stub support so far, but this opens up the beginning of build testing.
