runtime(filetype): ft detection maybe wrong if 'fic' set for *.[CH]

So only set the filetype to cpp for *.C and *.H files, if
'fileignorecase' option is not set.

Signed-off-by: shane.xb.qian <shane.qian@foxmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/filetype.vim

@@ -1,7 +1,7 @@
 " Vim support file to detect file types
 "
 " Maintainer:	The Vim Project <https://github.com/vim/vim>
-" Last Change:	2023 Aug 10
+" Last Change:	2023 Dec 06
 " Former Maintainer:	Bram Moolenaar <Bram@vim.org>
 
 " Listen very carefully, I will say this only once
@@ -348,7 +348,7 @@ au BufNewFile,BufRead *.cypher			setf cypher
 " C++
 au BufNewFile,BufRead *.cxx,*.c++,*.hh,*.hxx,*.hpp,*.ipp,*.moc,*.tcc,*.inl setf cpp
 if has("fname_case")
-  au BufNewFile,BufRead *.C,*.H setf cpp
+	au BufNewFile,BufRead *.C,*.H if !&fileignorecase | setf cpp | endif
 endif
 
 " C++ 20 modules (clang)