MCS: move HeaderType enum outside of class definition

Move functions which compute number of blocks or bits depending on
header type and corresponding enum outside of GprsCodingScheme
class. This will allows us to use standard libosmocore value_sting
functions in upcoming patches for IA Rest Octet encoding/decoding.

Change-Id: Id0873f85e1f16a72e17e7fbc4ad76b194917067f
diff --git a/src/Makefile.am b/src/Makefile.am
index eb4a2bb..51b047e 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -63,6 +63,7 @@
 	rlc.cpp \
 	osmobts_sock.cpp \
 	gprs_codel.c \
+	coding_scheme.c \
 	gprs_coding_scheme.cpp \
 	egprs_rlc_compression.cpp