(w32_defined_color): Check for valid frame before

(w32_defined_color): Check for valid frame before
applying gamma correction. Eliminate dependency on frame elsewhere.
(w32_load_system_font): Switch FIXED_PITCH and VARIABLE_PITCH.
(w32_to_x_font): Use resx and resy not height_in and width_in.
(x_to_w32_font): Doc fix.
(xlfd_strip_height): New function to strip and return font height.
(w32_font_match): Compare height separately from rest of xlfd
spec, using xlfd_strip_height.