(IT_set_face): Compare highlighted face with the default

(IT_set_face): Compare highlighted face with the default
face, and invert colors if these faces' colors are identical.
(Fmsdos_remember_default_colors): Don't swap foreground and
background colors in initial_colors[].
(IT_set_frame_parameters): Don't swap frame's foreground and
background pixels.  If ALIST includes "(reverse . t)", swap
foreground-color and background-color properties in frame's
param_alist.  If the original frame's param_alist doesn't specify
the colors, store unspecified-fg and unspecified-bg, reversed if
required.