vim-patch:9.1.1140: filetype: m17ndb files are not detected (#32618)

Problem:  filetype: m17ndb files are not detected
Solution: detect m17ndb files as m17ndb filetype,
          include filetype, syntax and indent files for the
          new filetype (David Mandelberg).

References:

https://www.nongnu.org/m17n/manual-en/m17nDBFormat.html describes the
format. https://git.savannah.nongnu.org/cgit/m17n/m17n-db.git/tree/ has
examples of the files.

closes: vim/vim#16696

ed7d8e55ac

Also adjust the xkb parent pattern according to dev_vimpatch.txt.

Co-authored-by: David Mandelberg <david@mandelberg.org>

runtime/indent/m17ndb.vim

@@ -0,0 +1,14 @@
+" Vim indent file
+" Language:	m17n database
+" Maintainer:	David Mandelberg <david@mandelberg.org>
+" Last Change:	2025 Feb 21
+
+if exists("b:did_indent")
+  finish
+endif
+let b:did_indent = 1
+
+setlocal autoindent
+setlocal nosmartindent
+
+let b:undo_indent = "setlocal autoindent< smartindent<"