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: Ic075dd5a53cc76cf1b6aeca5c31db495882db915
diff --git a/.gitignore b/.gitignore
index 4a42306..2852b4d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -21,3 +21,5 @@
 *.la
 .deps
 .libs
+
+contrib/libasn1c.spec
diff --git a/configure.ac b/configure.ac
index 53720b9..8c93c3f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -75,4 +75,5 @@
         src/Makefile
         include/Makefile
         include/asn1c/Makefile
-        Makefile)
+        Makefile
+        contrib/libasn1c.spec)
diff --git a/contrib/libasn1c.spec b/contrib/libasn1c.spec.in
similarity index 96%
rename from contrib/libasn1c.spec
rename to contrib/libasn1c.spec.in
index e05b3e9..59098c3 100644
--- a/contrib/libasn1c.spec
+++ b/contrib/libasn1c.spec.in
@@ -12,12 +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/
-#
-
-
 Name:           libasn1c
-Version:        0.9.32.0
+Version:        @VERSION@
 Release:        0
 Summary:        Osmocon ASN.1 decoder and encoder library
 License:        BSD-2-Clause