Update runtime files
diff --git a/runtime/syntax/c.vim b/runtime/syntax/c.vim
index 50878a7..04b132d 100644
--- a/runtime/syntax/c.vim
+++ b/runtime/syntax/c.vim
@@ -1,7 +1,7 @@
" Vim syntax file
" Language: C
" Maintainer: Bram Moolenaar <Bram@vim.org>
-" Last Change: 2022 Oct 05
+" Last Change: 2023 Mar 08
" Quit when a (custom) syntax file was already loaded
if exists("b:current_syntax")
@@ -348,7 +348,10 @@
syn keyword cConstant SIGABRT SIGALRM SIGCHLD SIGCONT SIGFPE SIGHUP SIGILL SIGINT SIGKILL SIGPIPE SIGQUIT SIGSEGV
syn keyword cConstant SIGSTOP SIGTERM SIGTRAP SIGTSTP SIGTTIN SIGTTOU SIGUSR1 SIGUSR2
syn keyword cConstant _IOFBF _IOLBF _IONBF BUFSIZ EOF WEOF FOPEN_MAX FILENAME_MAX L_tmpnam
- syn keyword cConstant SEEK_CUR SEEK_END SEEK_SET TMP_MAX stderr stdin stdout EXIT_FAILURE EXIT_SUCCESS RAND_MAX
+ syn keyword cConstant SEEK_CUR SEEK_END SEEK_SET TMP_MAX EXIT_FAILURE EXIT_SUCCESS RAND_MAX
+ syn keyword cConstant stdin stdout stderr
+ " POSIX 2001, in unistd.h
+ syn keyword cConstant STDIN_FILENO STDOUT_FILENO STDERR_FILENO
" used in assert.h
syn keyword cConstant NDEBUG
" POSIX 2001