patch 9.1.0306: filetype: x11vnc config file is not recognized

Problem:  filetype: x11vnc config file is not recognized
Solution: Detect '.x11vncrc' as conf filetype
          (Wu, Zhenyu)

See: https://linux.die.net/man/1/x11vnc

closes: #14511

Signed-off-by: Wu, Zhenyu <wuzhenyu@ustc.edu>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/testdir/test_filetype.vim

@@ -162,7 +162,7 @@ def s:GetFilenameChecks(): dict<list<string>>
     cobol: ['file.cbl', 'file.cob', 'file.lib'],
     coco: ['file.atg'],
     conaryrecipe: ['file.recipe'],
-    conf: ['auto.master', 'file.conf'],
+    conf: ['auto.master', 'file.conf', '.x11vncrc'],
     config: ['configure.in', 'configure.ac', '/etc/hostname.file', 'any/etc/hostname.file'],
     confini: ['/etc/pacman.conf', 'any/etc/pacman.conf', 'mpv.conf', 'any/.aws/config', 'any/.aws/credentials', 'file.nmconnection'],
     context: ['tex/context/any/file.tex', 'file.mkii', 'file.mkiv', 'file.mkvi', 'file.mkxl', 'file.mklx'],

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    306,
 /**/
     305,
 /**/