Add fset-theme.{c,h} with the fset plugin contribution to the built-in
"light" theme: 47 overrides on fset.color.* options (line backgrounds,
selected-row tuning, title and value colors) tuned for a
light-background terminal.
The table is a NULL-terminated 2-column array of strings (no struct
wrapper, matching the pattern adopted for the irc contribution).
fset_theme_register builds a hashtable from the table and calls
weechat_theme_register; fset_theme_init() is called once from
weechat_plugin_init after fset_config_init / fset_config_read.
Default option values are NOT changed.
Allows for custom LIBDIR to specified with cmake builds. WEECHAT_LIBDIR
is used for a custom Weechat directory, or set from LIBDIR (as LIBDIR
used to be set).
Sébastien Helleu