qga: start a man page

Add a simple man page for the qemu agent.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
*squashed in review comments from Eric Blake <eblake@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
diff --git a/qemu-doc.texi b/qemu-doc.texi
index f1c38b6..ea9b3fb 100644
--- a/qemu-doc.texi
+++ b/qemu-doc.texi
@@ -412,6 +412,7 @@
 * vm_snapshots::              VM snapshots
 * qemu_img_invocation::       qemu-img Invocation
 * qemu_nbd_invocation::       qemu-nbd Invocation
+* qemu_ga_invocation::        qemu-ga Invocation
 * disk_images_formats::       Disk image file formats
 * host_drives::               Using host drives
 * disk_images_fat_images::    Virtual FAT disk images
@@ -505,6 +506,11 @@
 
 @include qemu-nbd.texi
 
+@node qemu_ga_invocation
+@subsection @code{qemu-ga} Invocation
+
+@include qemu-ga.texi
+
 @node disk_images_formats
 @subsection Disk image file formats