Fix building against libiconv

Downloaded from
https://github.com/kyak/openwrt-packages/blob/master/fbterm/patches/001-iconv.patch

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

--- a/src/lib/io.cpp
+++ b/src/lib/io.cpp
@@ -119,10 +119,10 @@ void IoPipe::setCodec(const s8 *up, cons
 	if (!strcasecmp(up, down)) return;
 
 	mCodecRead = iconv_open(up, down);
-	if (mCodecRead == (void*)-1) mCodecRead = 0;
+	if (mCodecRead == (iconv_t)(-1)) mCodecRead = 0;
 
 	mCodecWrite = iconv_open(down, up);
-	if (mCodecWrite == (void*)-1) mCodecWrite = 0;
+	if (mCodecWrite == (iconv_t)(-1)) mCodecWrite = 0;
 }
 
 #define BUF_SIZE 10240
--- a/src/lib/io.h
+++ b/src/lib/io.h
@@ -23,6 +23,7 @@
 
 #include "type.h"
 #include "instance.h"
+#include <iconv.h>
 
 class IoPipe {
 public:
@@ -47,7 +48,7 @@ private:
 	void writeIo(s8 *buf, u32 len);
 
 	s32 mFd;
-	void *mCodecRead, *mCodecWrite;
+	iconv_t mCodecRead, mCodecWrite;
 	s8 mBufRead[16], mBufWrite[16];
 	u32 mBufLenRead, mBufLenWrite;
 };
