Properly exclude non-Linux/MS Windows build of G313

While the Winradio G313 backend wasn't being compiled on a non-Linux
POSIX system, the register function in winradio.c was which caused an
error linking rigctl.  Also, the host_os test in the configure script
now looks for a string containg "*linux-gnu*" which accepts such systems
as the Raspberry Pi which is defined as "linux-gnueabihf".

Thanks to Lorenzo Simoncello, IW3HER, for reporting this build error on
the Raspberry Pi.

configure.ac

@@ -619,13 +619,17 @@ AS_CASE(["$host_os"],
         ],
 dnl As g313-posix.c has a hard dependency on linux/types.h
 dnl via linradio/wrg313api.h, disable compilation on other POSIX.
-        [ *linux-gnu ], [
+dnl (Certain systems have extra characters following "-gnu" such as
+dnl the Raspberry Pi which is "linux-gnueabihf"; presume that "linux-gnu"
+dnl is a sufficient test.)
+        [ *linux-gnu* ], [
              AM_CONDITIONAL(G313_LINUX_GNU, true)
              AM_CONDITIONAL(G313_WINDOWS, false)
         ],
         [
              AM_CONDITIONAL(G313_LINUX_GNU, false)
              AM_CONDITIONAL(G313_WINDOWS, false)
+             AC_DEFINE([OTHER_POSIX], [1], [Compilation on POSIX other than Linux])
         ])
 
 dnl If libdl is present, check for its header file.

winradio/winradio.c

@@ -252,11 +252,9 @@ DECLARE_INITRIG_BACKEND(winradio)
 #endif
 #endif
 
-	/* Not available on MS Windows */
-#ifndef _WIN32
-#ifndef __CYGWIN__
+	/* Available on Linux and MS Windows */
+#ifndef OTHER_POSIX
 	rig_register(&g313_caps);
-#endif
 #endif
 
 	return RIG_OK;