Ports: Add TiMidity++

Also add it as a dependency for the `SDL_mixer` and `SDL2_mixer` ports.

Eawpats GUS patches are installed as part of the port, because without
patches TiMidity++ is not able to generate any sound. The license for
these is "fameware", credit to Andrew Suffield:

  https://lists.debian.org/debian-legal/2002/09/msg00137.html

Ports/timidity/package.sh

@@ -0,0 +1,30 @@
+#!/usr/bin/env -S bash ../.port_include.sh
+port='timidity'
+useconfigure='true'
+version='2.15.0'
+files="https://netcologne.dl.sourceforge.net/project/timidity/TiMidity%2B%2B/TiMidity%2B%2B-${version}/TiMidity%2B%2B-${version}.tar.xz timidity-${version}.tar.xz 9eaf4fadb0e19eb8e35cd4ac16142d604c589e43d0e8798237333697e6381d39
+https://www.quaddicted.com/files/idgames/sounds/eawpats.zip eawpats.zip.no_extract 19087fa4a40e25ec39a09cffcc9f775fc22d88bc971a7a9831e075cdae2ee1e3"
+auth_type='sha256'
+workdir="TiMidity++-${version}"
+use_fresh_config_sub='true'
+config_sub_paths=('autoconf/config.sub')
+depends=()
+configopts=(
+    'lib_cv___va_copy=no'
+    'lib_cv_va_copy=no'
+    'lib_cv_va_val_copy=no'
+)
+
+post_install() {
+    # Unpack Eawpats
+    eaw_pats_dir='/usr/local/share/eawpats'
+    eaw_pats_host_dir="${SERENITY_INSTALL_ROOT}${eaw_pats_dir}"
+    mkdir -p "${eaw_pats_host_dir}"
+    run unzip -qo -d "${eaw_pats_host_dir}" '../eawpats.zip.no_extract'
+
+    # Set up timidity.cfg
+    timidity_cfg_path="${SERENITY_INSTALL_ROOT}/etc/timidity.cfg"
+    mkdir -p "$(dirname ${timidity_cfg_path})"
+    cp "${eaw_pats_host_dir}/timidity.cfg" "${timidity_cfg_path}"
+    sed -i "s#^dir .*#dir ${eaw_pats_dir}#g" "${timidity_cfg_path}"
+}