media-sound/fluidsynth: bump to 2.0.4 with subslot, update ebuild

media-sound/fluidsynth: bump to 2.0.4 with subslot, update ebuild

Use subslot due to soversion change. Bump EAPI to 7. License is now LGPL-2.1+.
Add "oss" USE flag. Enable upstream-recommended USE flags by default (+readline
+sndfile). Drop versioned deps (no longer in portage.) Remove unused "ladcca"
cmake option. Put pkgconfig in BDEPEND. Remove forced "-pthread" flag.

Closes: https://bugs.gentoo.org/667254
Package-Manager: Portage-2.3.62, Repoman-2.3.12
Signed-off-by: Nikos Chantziaras <realnc@gmail.com>
Closes: https://github.com/gentoo/gentoo/pull/11257
Signed-off-by: Andreas Sturmlechner <asturm@gentoo.org>