encoding: Move the functions into the encoding class

Add some TODO to this class. E.g. they could all work on the
bitvec and the parameter handling could better.
diff --git a/src/gprs_rlcmac.cpp b/src/gprs_rlcmac.cpp
index edb2d1f..da48b6b 100644
--- a/src/gprs_rlcmac.cpp
+++ b/src/gprs_rlcmac.cpp
@@ -23,6 +23,7 @@
 #include <pcu_l1_if.h>
 #include <gprs_rlcmac.h>
 #include <bts.h>
+#include <encoding.h>
 #include <tbf.h>
 
 
@@ -304,7 +305,7 @@
 	LOGP(DRLCMAC, LOGL_NOTICE, "TX: [PCU -> BTS] Paging Request (CCCH)\n");
 	bitvec *paging_request = bitvec_alloc(23);
 	bitvec_unhex(paging_request, "2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b");
-	int plen = write_paging_request(paging_request, ptmsi, ptmsi_len);
+	int plen = Encoding::write_paging_request(paging_request, ptmsi, ptmsi_len);
 	pcu_l1if_tx_pch(paging_request, plen, (char *)imsi);
 	bitvec_free(paging_request);