query pixel size from matched font

Sorry for another duplicated mail. I found the patch is malformed
significantly. I've been away from my laptop for a while, so I'm quite
unfamiliar with the settings on this system...
Fix truecolor escapes, when both bg and fg are set

for example
echo -e "\e[48;2;255;0;0m\e[38;2;0;0;255m test "
should render on red bg with blue fg

also now elinks works correctly when using 'truecolor' option
in preferences

Signed-off-by: Amadeusz Sławiński <amade@asmblr.net>