patch 9.0.0218: reading before the start of the line

Problem:    Reading before the start of the line.
Solution:   When displaying "$" check the column is not negative.
diff --git a/src/proto/edit.pro b/src/proto/edit.pro
index a233e40..f35ec1e 100644
--- a/src/proto/edit.pro
+++ b/src/proto/edit.pro
@@ -5,7 +5,7 @@
 void edit_putchar(int c, int highlight);
 void set_insstart(linenr_T lnum, int col);
 void edit_unputchar(void);
-void display_dollar(colnr_T col);
+void display_dollar(colnr_T col_arg);
 void undisplay_dollar(void);
 void truncate_spaces(char_u *line);
 void backspace_until_column(int col);