Fix references to the no-longer-existent misc/ directory in comments, README files, and documentation

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

Add support for a union file system that can be used to overlay and merge the content of two mounted file systems.

Add basic board build configurat for the SAML21 Xplained.  Initial commit is jsut the SAMD20 Xplained with name changes and does not yet build

Update the type passed to watchdog timer handlers.  Using uint32_t is a problem for 64-bit machines.

OHCI:  Fix length calculation in all OHCI drivers:  CBP==0 means that the entire buffer was transferred, not that a null packet was tranaferred

Adds board support for the Teensy LC board.  Support is based off the Freedom KL25Z board. LED, PWM, and UART0 have been tested. The SPI pins are mapped correctly but have not yet been tested.  From Michael Hope as SourceForge patch 51.

Rename usbhost_storageinit() to usbhost_msc_initialize().  Add calls to usbhost_cdcacm_initialize() is CONFIG_USBHOST_CDCACM is selected.

Remove all traces of the Galileo board.  That port is not going to happen -- I dont' even have the Galileo board anymore.

Allow NSH date command with no RTC.  This command is useful without an RTC too.  Also, this permits testing on the simulator which never has an RTC

drawline/drawLine should not take a boolean to select non lines caps or capping at both ends.  drawline/drawLine also needs to be able to put a line cap on one one end of a line