Rename pic32-starterkit to pic32mx-starterkit to make room in the namespace for the pic32mz-starterkit

STM32: Fix for compilation introduced by last backup RAM change.  Not sure it it is correct, be now things do compile

Adds the ability to use the STM32F2 and STM32F4 Battery Backedup SRAM in the file system. With an option to Save Panic context to one of the files. From David Sidrane.

Changes to support fully write protecting the backup domain. N.B. stm32_pwr_enablebkp did not account for the delay from enable to the domain being writable. The KISS solution is a up_udelay. A more complex solution would be a negated write test with restore.  From David Sidrane.

Tiva: Move GPIIO prototypes out of arch/arm/include/tiva/irq.h to arch/arm/tiva/tiva_gpio.h where they belong

Fix some time value changes; mostly changing greater than 1000000000 to greater than or equal to 1000000000.  From Juha Niskanen

C++: Remove 'using ::timeval' from ctime.  struct timeval was recently move to sys/time.h where it belongs.  Now there are problems when it is referenced in ctime.  Fixed by just removing it from ctime.  Is that correct?  or should ctime include sys/time.h?  Noted by David Sidrane

VFS: The inode unlink method should not be support if operations on the root pseudo-filesystem are disabled.

this makes mkfatfs use fat_dma_alloc() when CONFIG_FAT_DMAMEMORY is
set. This is needed to ensure mkfatfs operates with boards that use
DMA for microSD

From Andrew Tridgell via the PX4/NuttX repository

Tiva: Updated files to allow for ADC triggering by the timer. I’ve cleaned up some parts of the ADC code, too, and fleshed out the PWM triggering ioctl.  From Calvin Maguranis

NSH: The default priority of the network initialization thread should be lower.  It is CPU intensive and can interfere with other operations