configure.ac (--enable-objc-gc): If not given, default to enable_objc_gc=no.

	* configure.ac (--enable-objc-gc): If not given, default to
	enable_objc_gc=no.
	* configure: Regenerated.

From-SVN: r243010
diff --git a/libobjc/configure.ac b/libobjc/configure.ac
index 0497836..89075c2 100644
--- a/libobjc/configure.ac
+++ b/libobjc/configure.ac
@@ -203,7 +203,7 @@
 AC_ARG_ENABLE(objc-gc,
 [AS_HELP_STRING([--enable-objc-gc],
 		[enable use of Boehm's garbage collector with the
-		 GNU Objective-C runtime])])
+		 GNU Objective-C runtime])],,enable_objc_gc=no)
 AC_ARG_WITH([target-bdw-gc],
 [AS_HELP_STRING([--with-target-bdw-gc=PATHLIST],
 		[specify prefix directory for installed bdw-gc package.