libpq: ccache -> credential cache

The term "ccache" is overloaded.  Let's be more clear, in case someone
other than a Kerberos wizard has to read this code.

src/interfaces/libpq/fe-connect.c

@@ -2748,13 +2748,13 @@ keep_going:						/* We will come back to here until there is
 #ifdef ENABLE_GSS
 
 				/*
-				 * If GSSAPI is enabled and we have a ccache, try to set it up
-				 * before sending startup messages.  If it's already
+				 * If GSSAPI is enabled and we have a credential cache, try to
+				 * set it up before sending startup messages.  If it's already
 				 * operating, don't try SSL and instead just build the startup
 				 * packet.
 				 */
 				if (conn->try_gss && !conn->gctx)
-					conn->try_gss = pg_GSS_have_ccache(&conn->gcred);
+					conn->try_gss = pg_GSS_have_cred_cache(&conn->gcred);
 				if (conn->try_gss && !conn->gctx)
 				{
 					ProtocolVersion pv = pg_hton32(NEGOTIATE_GSS_CODE);
@@ -2774,7 +2774,7 @@ keep_going:						/* We will come back to here until there is
 				else if (!conn->gctx && conn->gssencmode[0] == 'r')
 				{
 					appendPQExpBufferStr(&conn->errorMessage,
-										 libpq_gettext("GSSAPI encryption required, but was impossible (possibly no ccache, no server support, or using a local socket)\n"));
+										 libpq_gettext("GSSAPI encryption required, but was impossible (possibly no credential cache, no server support, or using a local socket)\n"));
 					goto error_return;
 				}
 #endif

src/interfaces/libpq/fe-gssapi-common.c

@@ -58,7 +58,7 @@ pg_GSS_error(const char *mprefix, PGconn *conn,
  * Check if we can acquire credentials at all (and yield them if so).
  */
 bool
-pg_GSS_have_ccache(gss_cred_id_t *cred_out)
+pg_GSS_have_cred_cache(gss_cred_id_t *cred_out)
 {
 	OM_uint32	major,
 				minor;

src/interfaces/libpq/fe-gssapi-common.h

@@ -20,7 +20,7 @@
 
 void		pg_GSS_error(const char *mprefix, PGconn *conn,
 						 OM_uint32 maj_stat, OM_uint32 min_stat);
-bool		pg_GSS_have_ccache(gss_cred_id_t *cred_out);
+bool		pg_GSS_have_cred_cache(gss_cred_id_t *cred_out);
 int			pg_GSS_load_servicename(PGconn *conn);
 
 #endif