Merge libitm changes to configure.ac from gcc master.

configure.ac

@@ -154,6 +154,7 @@ target_libraries="target-libgcc \
 		target-libgloss \
 		target-newlib \
 		target-libgomp \
+		target-libitm \
 		target-libstdc++-v3 \
 		target-libmudflap \
 		target-libssp \
@@ -492,6 +493,22 @@ if test x$enable_libgomp = x ; then
     esac
 fi
 
+# Disable libitm on unsupported systems.
+if test -d ${srcdir}/libitm; then
+    if test x$enable_libitm = x; then
+	AC_MSG_CHECKING([for libitm support])
+	if (srcdir=${srcdir}/libitm; \
+		. ${srcdir}/configure.tgt; \
+		test -n "$UNSUPPORTED")
+	then
+	    AC_MSG_RESULT([no])
+	    noconfigdirs="$noconfigdirs target-libitm"
+	else
+	    AC_MSG_RESULT([yes])
+	fi
+    fi
+fi
+
 # Disable libssp for some systems.
 case "${target}" in
   avr-*-*)