Detect availability of QEMU -chardev CLI option

* src/qemu/qemu_conf.h: defines a new QEMUD_CMD_FLAG_CHARDEV flag
* src/qemu/qemu_conf.c: parse the output for -chardev and set flag
  appropriately

src/qemu/qemu_conf.c

@@ -894,6 +894,8 @@ static unsigned int qemudComputeCmdFlags(const char *help,
         flags |= QEMUD_CMD_FLAG_PCIDEVICE;
     if (strstr(help, "-mem-path"))
         flags |= QEMUD_CMD_FLAG_MEM_PATH;
+    if (strstr(help, "-chardev"))
+        flags |= QEMUD_CMD_FLAG_CHARDEV;
 
     if (version >= 9000)
         flags |= QEMUD_CMD_FLAG_VNC_COLON;

src/qemu/qemu_conf.h

@@ -72,6 +72,7 @@ enum qemud_cmd_flags {
     QEMUD_CMD_FLAG_DRIVE_SERIAL  = (1 << 19), /* -driver serial=  available */
     QEMUD_CMD_FLAG_XEN_DOMID     = (1 << 20), /* -xen-domid (new style xen integration) */
     QEMUD_CMD_FLAG_MIGRATE_QEMU_UNIX = (1 << 21), /* Does qemu support unix domain sockets for migration? */
+    QEMUD_CMD_FLAG_CHARDEV       = (1 << 22), /* Is the new -chardev arg available */
 };
 
 /* Main driver state */