Add a wrapper header, mylcd.h, in the lib subdirectory, which lets plugins' code...

Add a wrapper header, mylcd.h, in the lib subdirectory, which lets plugins' code automatically call the proper functions depending if compilation is for greylib or color display, also forms proper call to grey_ and  xlcd_. mylcd_ub_ call greylib unbuffered routines, regular lcd routines otherwise. Form is mylcd_<fnname>, <fnname> is the symbol name stripped of prefixes lcd_, grey_, or xlcd_. Convert a couple plugins I know well (easy job).

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@26542 a1c6a512-1295-4272-9138-f99709370657