MCS: add mcs_is_*() helpers

In preparation for Channel Coding Command encoder in follow-up patches
let's add necessary helpers. Those are similar to previously used
helpers from GprsCodingScheme class but without CamelCase and with less
typo chances between Gprs and Egprs cases.

Change-Id: I6699cbc8d7ae766fa4d2b3d37e5f9ff1cf158b7e
diff --git a/src/coding_scheme.h b/src/coding_scheme.h
index f69a76e..3a9ef25 100644
--- a/src/coding_scheme.h
+++ b/src/coding_scheme.h
@@ -33,6 +33,10 @@
 extern const struct value_string mcs_names[];
 const char *mcs_name(enum CodingScheme val);
 
+bool mcs_is_gprs(enum CodingScheme cs);
+bool mcs_is_edge(enum CodingScheme cs);
+bool mcs_is_edge_gmsk(enum CodingScheme cs);
+
 enum HeaderType {
 	HEADER_INVALID,
 	HEADER_GPRS_CONTROL,