Cleanup iconv.

Cleanup iconv.

Implement -c, fix endless loop when illegal char happens with
!outleft (don't need to check errno, just in == toybuf), refill
buffer each time (less efficient handling of illegal chars but never
have to worry about how long constitutes a valid sequence in unknown
encoding).

Fix input longer than 2k (memmove() has src/dest switched, second time through
loop in starts at offset inleft...) Made it start at beginning every time.

Switch iconv_open() error msg to show to/from and errno (rather than
hardwired english text).