SAMA5:  Hook RTC into build system; Finish RTC alarm logic; Verify correct behavior of the basic RTC functionality

Add instructions to enable RTC in the nsh/ configuration; RTC enabled by default in the demo configuration

SAMA5 LCD:  Move framebuffers to center of free memory region.  That creates a guard band around the framebuffers that gives a little protection from any bad writes into the framebuffer

Enhanced the FAT32 filesystem code to understand DMA preflight failures, and to use the file sector buffer as a bounce buffer when a user-supplied buffer is not suitable for DMA. From Mike Smith

Enhanced the mmcdd_sdio driver to perform DMA preflight operations and fail DMA read/write requests that fail preflighting. From Mike Smith

Minor tweaks to debug output; started renaming some icons to include size in the name; SAMA5 NxWM config needs libm

New touchscreen scaling algorithm for the case where measured X values vary with y position (and vice versa)

net_sendfile:  Let the ACK callback handle the REXMIT flag and don't return until all data has been ACK'd. From Max Holtzberg

Move tcp connection into SYN_RCVD state after aception instead of bypassing and moving directly into ESTABLISHED.  From Max Holtzberg.