[binutils-gdb] Remove cleanup_iconv

[sergiodj+buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT 80a3b8c578e93119183db5f5e34248f843e410a7 ***

Author: Tom Tromey <tom@tromey.com>
Branch: master
Commit: 80a3b8c578e93119183db5f5e34248f843e410a7

Remove cleanup_iconv

This introduces a new "iconv_wrapper" class, to be used in
convert_between_encodings.  This allows the removal of cleanup_iconv.

gdb/ChangeLog
2017-04-12  Tom Tromey  <tom@tromey.com>

	* charset.c (iconv_wrapper): New class.
	(cleanup_iconv): Remove.
	(convert_between_encodings): Use it.