Properly handle goto blocks

[chirsz-ever]

I found a lot of rust code like that:

It should be replaced by some code without the match middle layer.

[crlf0710]

These magic numbers are generated by the c2rust tool. The number represent a "control flow block" which may be a goto destination in the original program. This definitely needs to be improved, but we need a good solution.

[mulimoen]

See also #140 for replacing a cleanup/panic goto with a function call

[burrbull]

@mulimoen can you take a look at xetex_xetex0::read_font_info?

[mulimoen]

Should be fairly straight forward by using a function bad_ftm() and done() at the end, and calling

return bad_ftm();

where

goto bad_ftm;

appears in the original source

[burrbull]

Functions still contain such current_blocks:

PR/Status	File	Function
	xetex_aatfont	loadAATfont
	xetex_xetex0	main_control
	xetex_linebreak	try_break
		hyphenate
	bibtex.rs	x_change_case
		x_format_name
		get_bib_command_or_entry_and_process
	xetex_ext	loadOTfont
	dpx_pdfobj	parse_xref_stream
		read_xref

[chirsz-ever]

Functions still contains current_blocks:

Some of the functions are still being rewote in progress, the removal of current_block would disturb other's work. They could be solved in other works conveniently instead of seperated PRs.