patch 8.2.2206: :exe command line completion only works for first argument

Problem:    :exe command line completion only works for first argument.
Solution:   Skip over text if more is following. (closes #7546)
diff --git a/src/eval.c b/src/eval.c
index e4149ab..e612070 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -1904,6 +1904,24 @@
 	    while ((c = *++arg) != NUL && (c == ' ' || c == '\t'))
 		/* skip */ ;
     }
+
+    // ":exe one two" completes "two"
+    if ((cmdidx == CMD_execute
+		|| cmdidx == CMD_echo
+		|| cmdidx == CMD_echon
+		|| cmdidx == CMD_echomsg)
+	    && xp->xp_context == EXPAND_EXPRESSION)
+    {
+	for (;;)
+	{
+	    char_u *n = skiptowhite(arg);
+
+	    if (n == arg || IS_WHITE_OR_NUL(*skipwhite(n)))
+		break;
+	    arg = skipwhite(n);
+	}
+    }
+
     xp->xp_pattern = arg;
 }