Add proper fullname for named-instances

Try to build a fullname from a family and a style name for a named-instance.

Fixes fontconfig/fontconfig#185
3 jobs for issue/185 in 5 minutes and 29 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #1094199
mingw-build

00:04:06

passed #1094197
shared-build

00:05:29

passed #1094198
static-build

00:03:49