Optimize request buffer sizes in the serial USB drivers so that we avoid so many NULL packets and so that the OUT request buffer size is exactly the max packet size.

Fix STM32F1 and F3 USB device driver.  It was not handling NULL packets correctly and it prevent use of the driver with the CDC/ACM class

Fix null packet handling in the PIC32 USB device driver.  This is a critical bug fix for PIC32.  Add support for the USB monitor to the Sure-PIC32MX configuration

Rename SLCD geometry tructure to attributes;  Move MAX contrast to attributes.  Add  attribute and ioctl commands to get and set SLCD brightness

Converted all configurations to use the kconfig-frontends tools, cleaned up the directory structure and naming to match some of the more recent configurations, and added a segment LCD driver for the board.  The initial checkin of the LCD driver is just a clone of configs/pcblogic-pic32mx/src/pic32mx_lcd1602 and it not yet expected to be functional.

PCB-Logic PIC32MX LCD1602 driver now supports SLCD CODED; Added an SLCD ioctl command to get cursor position

Converted configs/pcblogic-pic32mx configurations to use kconfig-frontends.  Re-organization of files in configs/pcblogic-pic32mx/src

Additional bug fixes and minor extensions to the STM32L-Disovery segment LCD support and to the apps/examples/slcd segment LCD test.

Add apps/examples/slcd, Remove USB from STM32L-Discovery, LSE support for the STM32 L family, some STM32L-Discovery LCD debug changes

Fix STM32L15X vector definitions; Fix STM32L-Discovery LED controls.  The NSH configuration is now fully functional on the STM32L-Discovery board.

Add audio/ sub-syste, include/nuttx/audio.h interface, and drivers/audio/vs1053.c driver to NuttX.  From Ken Pettit