contrib: integrate RPM spec

Remove OpenSUSE bug report link, set version to @VERSION@, make it build
with CentOS 8 etc.

Related: OS#4550
Change-Id: I8b4646ffc8c79d717ada2f0d8da14a721000c2e4

.gitignore

@@ -58,3 +58,5 @@ jibuf_tool
 osmux_test2
 stream_test
 amr_test
+
+contrib/libosmo-netif.spec

configure.ac

@@ -133,4 +133,5 @@ AC_OUTPUT(
 	examples/Makefile
 	tests/Makefile
 	Doxyfile
-	Makefile)
+	Makefile
+	contrib/libosmo-netif.spec)

contrib/libosmo-netif.spec.in

@@ -12,13 +12,8 @@
 # license that conforms to the Open Source Definition (Version 1.9)
 # published by the Open Source Initiative.
 
-# Please submit bugfixes or comments via http://bugs.opensuse.org/
-#
-
-
-%define version_unconverted 0.7.0.13
 Name:           libosmo-netif
-Version:        0.7.0.13
+Version:        @VERSION@
 Release:        0
 Summary:        Osmocom library for muxed audio
 License:        GPL-2.0-or-later