stm32f1: Add missing peripheral base address for F100
Clarify toolchains and install steps

Including removing the extremely unhelpful DETECT_TOOLCHAIN option.
sync: use matching #ifdefs in source as in header

Fixes github issue #298
stm32f1: Fix RCC CAN defines

Thanks to Марко Краљевић <krasnaya.zvezda@gmail.com>
[f3] add USART_SR_x defines for common status flags

enables the use of usart_get_flag(USARTx, USART_SR_x) on F3 just like on F124

closes #283
libopencmsis: Fill in missing CMSIS interrupt links

And correct a minor typo in the generated code.
stm32/flash: Make comments match reality

Copy/paste commentary with wrong sizes.
stm32/dac: Follow ref-man guidelines on GPIO config

GPIO pins should be configured for Analog IN on virtually all families
to reduce parasitic consumption.

Reported-by: Roger Wolff <R.E.Wolff@BitWizard.nl>
Merge remote-tracking branch 'upstream/master' into spidefsfix