Extend the OS detection to non Windows platforms

At the moment, only the Windows platform needs some special handling,
but this can easily be extended to detect and handle other platforms as
well.

configure.ac

@@ -72,18 +72,18 @@ AM_CONDITIONAL([HAVE_MANDOC],[test -n "$MANDOC"])
 # Enable automake silent build rules.
 m4_ifdef([AM_SILENT_RULES],[AM_SILENT_RULES([yes])])
 
-# Checks for native Windows.
-AC_MSG_CHECKING([for native Win32])
+# Checks for operating system.
+AC_MSG_CHECKING([for operating system])
 case "$host" in
   *-*-mingw*)
-    os_win32=yes
+    platform=windows
     ;;
   *)
-    os_win32=no
+    platform=default
     ;;
 esac
-AC_MSG_RESULT([$os_win32])
-AM_CONDITIONAL([OS_WIN32], [test "$os_win32" = "yes"])
+AC_MSG_RESULT([$platform])
+AM_CONDITIONAL([OS_WIN32], [test "$platform" = "windows"])
 
 DEPENDENCIES=""
 
@@ -192,7 +192,7 @@ AX_APPEND_COMPILE_FLAGS([ \
 ])
 
 # Windows specific compiler options.
-AS_IF([test "$os_win32" = "yes"], [
+AS_IF([test "$platform" = "windows"], [
 	AX_APPEND_COMPILE_FLAGS([-Wno-pedantic-ms-format])
 ])