game-music-emu: various improvements

Add missing zlib dependency. Remove SDL2 dep since the demo program
that uses it is not installed anyway. Also don't bother building it
even if SDL is found. Use release tarball.

audio/game-music-emu/Portfile

@@ -5,8 +5,8 @@ PortGroup           cmake   1.1
 PortGroup           github  1.0
 
 github.setup        libgme game-music-emu 0.6.4
-github.tarball_from archive
-revision            0
+github.tarball_from releases
+revision            1
 
 homepage            ${homepage}/wiki
 
@@ -19,11 +19,15 @@ license             GPL-3
 maintainers         {gmail.com:herby.gillot @herbygillot} \
                     openmaintainer
 
-checksums           rmd160  72c84c52b52f1979fb49b57a261feb51e5047925 \
-                    sha256  f2360feb5a32ace226c583df4faf6eff74145c81264aaea11e17a1af2f6f101a \
-                    size    343669
+distname            libgme-${version}-src
+worksrcdir          libgme-${version}
+checksums           rmd160  98bb96c7da564e4619612a40b5c55e2c9963e61b \
+                    sha256  6f94eac735d86bca998a7ce1170d007995191ef6d4388345a0dc5ffa1de0bafa \
+                    size    343689
 
 depends_build-append \
                     port:pkgconfig
 
-depends_lib-append  port:libSDL2
+depends_lib-append  port:zlib
+
+configure.args-append   -DGME_BUILD_EXAMPLES=OFF