STL32 F15x: stm32_stdclockconfig() was calling stm32_pw_setvos() which accessed PWR_CR via an inactive APB. From Juha Niskanen.

Add support for MK20DN--VLH5 and MK20DX---VLH5.  Needed for backward compatible support for Teensy-3.0

SAML21: Since SERCOM5 usese a different output channel, it will also need a different GCLK generator

Documentation:  Add target=_blank to some URLs so they can be opened from DocuWiki.  Some Sourceforge content cannot be served in a frame