patch 9.1.1173: filetype: ABNF files are not detected

Problem:  filetype: ABNF files are not detected
Solution: detect '.abnf' file as abnf filetype and
          include an abnf syntax plugin (A4-Tacks).

References:
- RFC5234
- RFC7405

closes: #16802

Signed-off-by: A4-Tacks <wdsjxhno1001@163.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_filetype.vim b/src/testdir/test_filetype.vim
index bbc2d1f..d8fc0a1 100644
--- a/src/testdir/test_filetype.vim
+++ b/src/testdir/test_filetype.vim
@@ -87,6 +87,7 @@
     abap: ['file.abap'],
     abc: ['file.abc'],
     abel: ['file.abl'],
+    abnf: ['file.abnf'],
     acedb: ['file.wrm'],
     ada: ['file.adb', 'file.ads', 'file.ada', 'file.gpr'],
     ahdl: ['file.tdf'],
diff --git a/src/version.c b/src/version.c
index cfb661e..8b42a79 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1173,
+/**/
     1172,
 /**/
     1171,