net/drivers/skeleton.c:  Back out serialization changes of the last commit.  They are not necessary in the skeleton.c example because the calls to net_lock() at the beginning of each worker function will enforce serialization.

drivers/net:  Add framework for serialization in the case where multiple low-priority work queues are used.

Revert "FS:  Fix backward conditional logic that prevent unlink() from building in some configurations."

Oops.  It was not backward.  Enable == !Disable.  Negative logic is confusing.

This reverts commit 1fcf353e.

fixed a typo

Approved-by: Gregory Nutt

Experimental change to STM32 Ethernet driver a success.  Porting change to all other Ethernet drivers.

Implements support for smaller interrupt tables as described at http://www.nuttx.org/doku.php?id=wiki:howtos:smallvectors .  This is largely the work of Mark Schulte.  However, I have made several changes to match with the Wiki document.  If you like the change, thanks go to Marc.  For any errors you can blame me.

Revert "CONFIG_START_YEAR/MONTH/DAY not required if an RTC is used"

Approved-by: Gregory Nutt

This reverts commit 4035ed8c.

stm32_gpiosetevent: GPIO IRQ function should not return the xcpt_t oldhandler.  This value is useful and potentially dangerous by itself after the change to assocaite a argument with the interrupt handler.

stm32_gpiosetevent: GPIO IRQ function should not return the xcpt_t oldhandler.  This value is useful and potentially dangerous by itself after the change to assocaite a argument with the interrupt handler.

stm32_gpiosetevent: GPIO IRQ logic no longer returns the xcpt_t oldhandler.  This value is useless and dangerous after the recent changes to interrupt argument passing.

board_button_irq: Button IRQ logic no longer returns the xcpt_t oldhandler.  There value is useless and dangerous after the recent changes to interrupt argument passing.

board_button_irq: Button IRQ logic no longer returns the xcpt_t oldhandler.  There value is useless and dangerous after the recent changes to interrupt argument passing.

board_button_irq: Button IRQ logic no longer returns the xcpt_t oldhandler.  There value is useless and dangerous after the recent changes to interrupt argument passing.

Tiva: Pin IRQ logic no longer returns the xcpt_t oldhandler.  There value is useless and dangerous after the recent changes to interrupt argument passing.

STM32 L4: Pin IRQ logic no longer returns the xcpt_t oldhandler.  There value is useless and dangerous after the recent changes to interrupt argument passing.

PIC32MZ: Pin IRQ logic no longer returns the xcpt_t oldhandler.  There value is useless and dangerous after the recent changes to interrupt argument passing.

PIC32MX: Pin IRQ logic no longer returns the xcpt_t oldhandler.  There value is useless and dangerous after the recent changes to interrupt argument passing.