add -machine mem-merge=on|off option

It allows to disable memory merge support (KSM on Linux), which is
enabled by default otherwise.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/qemu-config.c b/qemu-config.c
index eba977e..12eafbb 100644
--- a/qemu-config.c
+++ b/qemu-config.c
@@ -615,6 +615,10 @@
             .name = "dump-guest-core",
             .type = QEMU_OPT_BOOL,
             .help = "Include guest memory in  a core dump",
+        }, {
+            .name = "mem-merge",
+            .type = QEMU_OPT_BOOL,
+            .help = "enable/disable memory merge support",
         },
         { /* End of list */ }
     },