net/icmpv6:  Fix an error in the poll logic.  It was assume that the input parmeter pvconn was valid.  It was not.  Instead, the poll logic must work like the sendto() and recvfrom() logic:  It must keep a copy of the conn structure in the private data.

Replicate Jussi Kivilinna's change for the newly added STM32F2xx and F3xx family members.  This change allows selecting voltage output scale mode and enable over-drive only when needed.

1) The first enables building with CONFIG_ARCH_IDLE_CUSTOM enabled.
2) The second allows changing voltage output scaling setting and prevents enabling over-drive mode for low frequencies (STM32 F74xx, 75xx, 76xx, 77xx)

STM32, STM32 L4, and STM32 M4: USB OTGFS DMA trace output fix
STM32: Add dump buffer feature to stm32 F4 series
STM32 and STM32 L4: Fix bad USB OTGFS register address
STM32 L4:  Fix typo in USB OTGFS register usage
STM32 L4:  Add check in USB OTGFS driver to assure that SYSCFG is enabled
Nucleo-L496ZG:  Make HSE on Nucleo-L496ZG default to enable USB

net/sixlowpan:  The logic that extracts interface identifier from the IP address needs to be generalized to handle cases where the address is not a link local address.

configs/open1788:  Enable discrete joystick input.  This is sufficient to get through all menuing that does not require text input.

net/icmpv6:  icmpv6_input() needs to set d_len to 0 after consuming echo reply, otherwise, garbage will get sent out.

configs/open1788:  Add support for the discrete joystick driver.  Update the pdcurses configuration to use apps/examples/djoystick.

Fix sscanf character conversion (%c): do not add '\0' at the end as for strings, cause, for example, parsing one character will fill two bytes: character itself and zero one '\0' after it, so will overflow one byte variable argument and corrupt memory for variables allocated after it.

    libnx/nxfonts:  Cosmetic; reduce amount of debug output.
    configs/open1788/pdcurses:  Add a configuration for testing pdcurses.

Changes to allow the font subsystem to be built without enabling the entire graphics system (CONFIG_NX).  Adds CONFIG_NXFONTS and CONFIG_NXGLIB.  NX and NXFONTS are still pretty heavily entangled

Squashed commit of the following:

    libnx: Need to duplicate some Kconfig setting for NXFONTs if it can be configured and built independently of NX.  Also includes some build-related fixes.

    configs/sim:  Disable NX graphics support in the fb configuration.

    libnx:  Basic configuration and build changes to support building font support independend of the NX server.

STM32F7:  Completes architecture support for the STM32 F72x and F73x families.  Adds support for the Nucleo-144 boards with STM32F722.

configs/stm3220g-eval/ide:  Remove the uVision IDE setup.  This has not been used for years and it a maintenance problem for me.

configs/stm32f429i-disco/ide:  Remove the uVision IDE setup that goes along with the ltdc configuration that was removed on 2017-10-28.

STM32F429i-Disco: Convert NxWM configuration to use LTDC framebuffer driver instead of SPI serial.  Also reduce number of layers from 4 to 1 in fb configuration.  Only one layer is used.

Build system:  Fix CONFIG_BUILD_KERNEL logic directories that have ubin and kbin subdirectories.  Conditional logic was fine for CONFIG_BUILD_FLAT and CONFIG_BUILD_PROTECTED but generated useless dependencies if CONFIG_BUILD_KERNEL.

arch/arm/src/lpc43: UART_RX pins should be configured with input buffers enabled. Otherwise it cannot be read.

Build system:  Fix CONFIG_BUILD_KERNEL logic directories that have ubin and kbin subdirectories.  Conditional logic was fine for CONFIG_BUILD_FLAT and CONFIG_BUILD_PROTECTED but generated useless dependencies if CONFIG_BUILD_KERNEL.