varobj zero-padded hexadecimal format

varobj zero-padded hexadecimal format

This set of patches add support for the zero-padded hexadecimal format for
varobj's, defined as "zero-hexadecimal".  We currently only support regular
non-zero-padded hexadecimal.

Talking with IDE developers, they would like to have this option that is
already available to GDB's print/x commands, in the CLI, as 'z'.

gdb/ChangeLog:

2015-12-09  Luis Machado  <lgustavo@codesourcery.com>

	* gdb/mi/mi-cmd-var.c (mi_parse_format): Handle new "zero-hexadecimal"
	format.
	* gdb/varobj.c (varobj_format_string): Add "zero-hexadecimal" entry.
	(format_code): Add 'z' entry.
	(varobj_set_display_format): Handle FORMAT_ZHEXADECIMAL.
	* gdb/varobj.h (varobj_display_formats) <FORMAT_ZHEXADECIMAL>: New enum
	field.
	* NEWS: Add new note to MI changes citing the new zero-hexadecimal
	format for -var-set-format.

gdb/doc/ChangeLog:

2015-12-09  Luis Machado  <lgustavo@codesourcery.com>

	* gdb.texinfo (GDB/MI Variable Objects): Update text to mention
	-var-set-format's new zero-hexadecimal format.

gdb/testsuite/ChangeLog:

2015-12-09  Luis Machado  <lgustavo@codesourcery.com>

	* gdb.mi/mi-var-display.exp: Add new checks for the zero-hexadecimal
	  format and change test names to make them unique.