classes/package(prserv).bbclass: Get PRAUTO and use PKGV/PKGR.

1. Added package_get_auto_pr to PACKAGEFUNCS to get the auto
incremented value(PRAUTO) from remote PR service.

2. use PKGV/PKGR for pkgdata which will be used by package_write_xxx.

3. Added supporting functions in prserv.bbclass.

(From OE-Core rev: b1f6120c04731d3d66f322ce550b0d223c118dab)

Signed-off-by: Lianhao Lu <lianhao.lu@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/prserv.bbclass

@@ -0,0 +1,29 @@
+def prserv_make_conn(d):
+    import prserv.serv
+    host=d.getVar("PRSERV_HOST",True)
+    port=d.getVar("PRSERV_PORT",True)
+    try:
+        conn=None
+        conn=prserv.serv.PRServerConnection(host,int(port))
+        d.setVar("__PRSERV_CONN",conn)
+    except Exception, exc:
+        bb.fatal("Connecting to PR service %s:%s failed: %s" % (host, port, str(exc)))
+
+    return conn
+
+def prserv_get_pr_auto(d):
+    if not d.getVar('USE_PR_SERV', True):
+        bb.warn("Not using network based PR service")
+        return None
+
+    conn=d.getVar("__PRSERV_CONN", True)
+    if conn is None:
+        conn=prserv_make_conn(d)
+        if conn is None:
+            return None
+
+    version=d.getVar("PF", True)
+    checksum=d.getVar("BB_TASKHASH", True)
+    auto_rev=conn.getPR(version,checksum)
+    bb.debug(1,"prserv_get_pr_auto: version: %s checksum: %s result %d" % (version, checksum, auto_rev))
+    return auto_rev