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.
