Export missing function from libztex.

libztex.h

@@ -98,5 +98,6 @@ extern int libztex_setFreq (struct libztex_device *ztex, uint16_t freq);
 extern int libztex_sendHashData (struct libztex_device *ztex, unsigned char *sendbuf);
 extern int libztex_readHashData (struct libztex_device *ztex, struct libztex_hash_data nonces[]);
 extern int libztex_resetFpga (struct libztex_device *ztex);
+extern int libztex_selectFpga(struct libztex_device *ztex, int number);
 
 #endif /* __LIBZTEX_H__ */