Fixes for -Wmissing-declarations and -Wwrite-strings warnings.

diff --git a/programs/winhelp/macro.c b/programs/winhelp/macro.c
index 71efad4..e34a4dc 100644
--- a/programs/winhelp/macro.c
+++ b/programs/winhelp/macro.c
@@ -33,10 +33,10 @@
 /*               Macro table                      */
 /**************************************************/
 struct MacroDesc {
-    char*       name;
-    char*       alias;
+    const char* name;
+    const char* alias;
     BOOL        isBool;
-    char*       arguments;
+    const char* arguments;
     FARPROC     fn;
 };