Revert "Revert "librtmp.recipe: Use same version as gentoo""

This reverts commit 2f6d65b03bafb23df429a6a4b9e726a7ff55333f and fixes
cross-compilation by adding a new patch to the build system. Original commit
message:

    Since there's been no release of librtmp in ages (there isn't even a
    official 2.4 tarball), use the same version as gentoo is using.

    The tarball is temporarily stored on my personal fdo folder until we
    figure out a better solution.

    It is the same content as a9f353c7ccf29d6305e13fedb77653b8681e9fc2
    on git://git.ffmpeg.org/rtmpdump

    also ensure libgpg-error is rebuilt if gnutls changed
New recipe: openssl.recipe

The Android build fails to compile right now
New recipe: libsrtp.recipe
glib.recipe: Include glib-gettext.m4 in devel files
New recipe: vala-m4.recipe

Contains the m4 macros needed during autoreconf by configure files that use
VAPIGEN_CHECK
New recipe: gobject-introspection-m4.recipe
librsvg: Fix automagic gtk+ support, and add missing gdk-pixbuf dep
New recipe: openh264.recipe
gst-plugins-bad-1.0: Add srtp and openh264 plugins
New recipe: icu.recipe

Cross-compilation is complicated, so has been left alone for now
harfbuzz.recipe: Now that we have ICU, we can actually build with ICU support
New recipe: libsusrsctp.recipe
New recipe: gnome-js-common.recipe
New recipe: javascriptcoregtk.recipe

Lots of hacks to build only JSC and not WebKit-GTK+
New recipe: seed.recipe
New recipe: libnice.recipe
New recipe: openwebrtc-gst-plugins.recipe
New recipe: openwebrtc.recipe