VNC: Fixes from debug.  One issues is that VNC client is changing color formats after starting.  That is now handled.

STM32F7:  Add dummy stm32_spi.h header file to workaround some compilation issues.  Suggest by Martin Davey.

lpc4357fet256_pinconfig.h has wrong ethernet pins configuration (slow slew rate, somewhere inbuffer should be used). From Vytautas Lukenskas

QSPI interrupt driven mode is now implemented

Backout 3f731241.  It is a good idea, but has some unpleasant side effect... like SYSLOG and dbg() no longer work

Add handshake to coordintate with connection of VNC client.  fb_initialize() will not return until the connection is established

basic support for QSPI in STM32L4; verified via 'examples/media'