Fix linking with libiconv

Inspired by https://github.com/el1n/OpenWRT-package-softether/blob/4cb1cd9073a76edf34c512e587069626e02e2404/patches/120-fix-iconv-headers-common.patch

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>

Index: b/src/Mayaqua/Mayaqua.h
===================================================================
--- a/src/Mayaqua/Mayaqua.h
+++ b/src/Mayaqua/Mayaqua.h
@@ -282,17 +282,7 @@
 #include <ifaddrs.h>
 #endif	// MAYAQUA_SUPPORTS_GETIFADDRS
 
-#ifdef	UNIX_LINUX
-typedef void *iconv_t;
-iconv_t iconv_open (__const char *__tocode, __const char *__fromcode);
-size_t iconv (iconv_t __cd, char **__restrict __inbuf,
-                     size_t *__restrict __inbytesleft,
-                     char **__restrict __outbuf,
-                     size_t *__restrict __outbytesleft);
-int iconv_close (iconv_t __cd);
-#else	// UNIX_LINUX
 #include <iconv.h>
-#endif	// UNIX_LINUX