GitLab

* src/termhooks.h (defined_color_hook): New terminal hook.

* src/xterm.c:
* src/nsterm.m:
* src/term.c:
* src/w32term.c: Set defined_color_hook.

* src/xfaces.c: Use defined_color_hook.
(defined_color): Remove.

* src/image.c: Remove redefinitions of x_defined_color, and use
defined_color_hook.