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).
F2 and F4 have a common section to deal with the options register (TIM2 and TIM5 only)
L1 has been made common with timer_common_all as its options register has very different settings to F2/F4. Code is in the L1/timer.c L1/timer.h files
Note that F3 and F05 timers should fit into this scheme, with F3 having additional features.
Bundled with this is L1/pwr.h to change a documentation setting
Also all the Doxyfiles have added "ENABLE_PREPROCESSING = NO" to fix a problem introduced by commit 118.
New doc directory with config files and generated html, LaTeX/pdf.
Makefile provided for autogeneration and explanatory README.
The project structure is hostile to doxygen, which can't cope with functions
of the same name. Doxygen is run for each family separately, and separately
for LaTeX generation. Customized layout files sort of "integrate" HTML, and
separate pdfs are generated for each family. Not ideal but seems the best
solution until doxygen changes, if at all.
