(load_color): Remove static from definition and remove

(load_color): Remove static from definition and remove
prototype.
[MSDOS]: Add a DOS-specific version of load_color.
(lookup_face): Replace FRAME_TERMCAP_P with !FRAME_WINDOW_P.
(lookup_derived_face): New function.
(realize_default_face): Support MSDOS frames.
[MSDOS]: If fore/background colors are unspecified, inherit them
from the frame.
(realize_face): Support MSDOS frames.
(realize_tty_face): Support MSDOS frames.
[MSDOS]: If the face color is not in Vface_tty_color_alist, call
load_color to try to find a suitable approximation.  If the face
is inverse-video, swap the foreground and background colors.