Turns out, there's lots of common code for flash. Pull up prefetch
on/off to start with, as there's only a single bit name different.
Pull up the definitions of common API functions too, starting with
flash_set_ws. Even if the implementations are different, things that
meant to be the same, should be defined centrally.
So that the navigation pane works correctly in browsers.
Some additional doc fixes put in where found (but many more still to go).
Added some dummy .c and .h files to bring the associated docs into line.
makefile changed to allow 'make html' as well as 'make doc' (the latter only does html anyway).
- Makefiles of other stm32s updated accordingly.
- f3/rcc.c updated to some definition changes.
- f3/flash.c removed in order to use flash_common_f234.c to comply with new organization.
