patch 8.0.1748: CmdlineEnter command uses backslash instead of slash

Problem:    CmdlineEnter command uses backslash instead of slash.
Solution:   Don't treat the character as a file name. (closes #2837)
diff --git a/src/fileio.c b/src/fileio.c
index f02925b..700bd3e 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -9524,6 +9524,12 @@
 	 * ColorScheme, QuickFixCmd* or DirChanged */
 	if (event == EVENT_FILETYPE
 		|| event == EVENT_SYNTAX
+		|| event == EVENT_CMDLINECHANGED
+		|| event == EVENT_CMDLINEENTER
+		|| event == EVENT_CMDLINELEAVE
+		|| event == EVENT_CMDWINENTER
+		|| event == EVENT_CMDWINLEAVE
+		|| event == EVENT_CMDUNDEFINED
 		|| event == EVENT_FUNCUNDEFINED
 		|| event == EVENT_REMOTEREPLY
 		|| event == EVENT_SPELLFILEMISSING
@@ -9532,7 +9538,10 @@
 		|| event == EVENT_OPTIONSET
 		|| event == EVENT_QUICKFIXCMDPOST
 		|| event == EVENT_DIRCHANGED)
+	{
 	    fname = vim_strsave(fname);
+	    autocmd_fname_full = TRUE; /* don't expand it later */
+	}
 	else
 	    fname = FullName_save(fname, FALSE);
     }