fix nasty bug in ISR handler, where interrupt was not properly acknowleged (write to CR instead of ISR, as intended).  Also, minor, set the LSI prescaler values more appropriately (though not critical since LSI is so low precision anyway).

correct the RTC_ALRMR_ENABLE value, it needs to ignore the date/dow component since that is not set.  Also, the prescaler value for HSE (which presumes 1 MHz, anyway) had transposed digits.

support for HSE and MSI clock sources; prelude to USB

booboo in config sanity check; wasn't preventing insanity

stm32l4-disco boardctls for qspi memmap; bugs found along the way

add board ioctls for allowing user application to cause qspi memory mapped mode to be engaged and disengaged.  Also partitioned qspi flash for filesystem and other purposes (eventually xip).

bug in smart.c; return code of smart_scan not checked, can cause success result in failure case, leading to 'dev' pointer being invalid.

add configuration options to allow SRAM2 to be used for heap, or not at all, and to zero-init it on OS start, or not at all.

add configuration options to allow SRAM2 to be used for heap, or not at all, and to zero-init it on OS start, or not at all.

QSPI DMA support in STM32L4, and DMA fixes...

fixed missing DMA peripheral selection and some header defines, updated various comments to be accurate