Add flow control support to the STM32 serial driver; Fix some issues with UART2 and 5.  From Lorenz Meier and Mike Smith

Add register definitions for SAM4L BPM and SCIF blocks; SAM4L clock initialization now selects an optimal  power scaling mode

If CONFIG_STM32_DMACAPABLE is defined, use stm32_dmacapable to workaround attempt SPI DMAs from the CCM stack

Add missing NSH configuration settings.  Correct some conditional logic for STM32 FALSH pre-fetch settings.  From Lorenz Meier

Eliminated sam3u_internal.h. Use separate header files instead.  More renaming from sam3u_ to sam_ to make room in the namespce for the sam4l_

Move SAM3U header files to arch/arm/src/sam3u/chip. Some renaming of SAM3U to SAM to ssupport SAM4.  Convert all configs/sam3u-ek configurations to use the kconfig-frontends tool

Upate .gitignore files.  Add .dSYM. Make sure / is present where needed.  Add some missing .gitignore files

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

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.

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.