Fix compilation with --disable-lzo and --disable-lz4

struct compress_options is defined under USE_COMP, therefore
compilation fails when it is referenced without that define.

Since function show_compression_warning, which uses aforementioned
struct, is only called under USE_COMP, it is safe to wrap its definition
under USE_COMP, which fixes compilation issue.

Trac: #1308

Signed-off-by: Lev Stipakov <[email protected]>
Acked-by: Gert Doering <[email protected]>
Message-Id: <[email protected]>
URL: https://www.mail-archive.com/[email protected]/msg20637.html
Signed-off-by: Gert Doering <[email protected]>

src/openvpn/options.c

@@ -5085,6 +5085,7 @@ set_user_script(struct options *options,
 #endif
 }
 
+#ifdef USE_COMP
 static void
 show_compression_warning(struct compress_options *info)
 {
@@ -5103,6 +5104,7 @@ show_compression_warning(struct compress_options *info)
         }
     }
 }
+#endif
 
 static void
 add_option(struct options *options,