Advance to 4.0~rc4

Per request of Mike, W9MDB, release RC4 up to commit
e1aa80599f on the master branch.

configure.ac

@@ -15,7 +15,7 @@ dnl however, the use of '~' should be fine as apt (others?) will treat
 dnl it as an earlier version than the actual release.  TNX KA6MAL
 dnl PACKAGE_NAME + " " + PACKAGE_VERSION must not exceed 20 chars!
 AC_INIT([Hamlib],
-	[4.0~rc3],
+	[4.0~rc4],
 	[hamlib-developer@lists.sourceforge.net],
 	[hamlib],
 	[http://www.hamlib.org])