Document language handling

FcConfigSubstitueWithPat's adding of default languages to pattern
FcFont[Set]Sort's language-aware sorting
3 jobs for lang_doc in 8 minutes and 54 seconds (queued for 3 minutes and 13 seconds)
latest
Status Job ID Name Coverage
  Build
passed #579407
mingw-build

00:04:28

passed #579405
shared-build

00:04:55

passed #579406
static-build

00:03:47