Fix phony_iconv wide character support.

Fix phony_iconv wide character support.

2016-01-15  Sandra Loosemore  <sandra@codesourcery.com>

	gdb/
	* charset.c [PHONY_ICONV] (GDB_DEFAULT_HOST_CHARSET):
	Conditionalize for Windows host.
	(GDB_DEFAULT_TARGET_CHARSET): Match GDB_DEFAULT_HOST_CHARSET.
	(GDB_DEFAULT_TARGET_WIDE_CHARSET): Use UTF-32.
	(phony_iconv_open): Handle both UTF-32 endiannesses.
	(phony_iconv): Likewise.  Check for output overflow and clean up
	out-of-input cases.  Correct adjustment to input buffer pointer.
	(set_be_le_names) [PHONY_ICONV]: Use hard-wired names to match
	phony_iconv_open.