Check charsets properly.
diff --git a/configure.ac b/configure.ac
index dfc6afa..b42d9b8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -60,7 +60,8 @@
AC_HEADER_TIME
# zlib.h the day we need to decompress firmware
AC_CHECK_HEADERS([ctype.h errno.h fcntl.h getopt.h libgen.h \
- limits.h stdio.h string.h sys/stat.h sys/time.h unistd.h iconv.h])
+ limits.h stdio.h string.h sys/stat.h sys/time.h unistd.h \
+ iconv.h langinfo.h])
AC_CHECK_HEADER([usb.h],,
AC_MSG_ERROR([I can't find the libusb header file on your system.
You may need to set the CPPFLAGS environment variable to include