Fix #3445: (latex) make \\usepackage[utf8x]{inputenc} usable

[jfbu]

Relates

• TeX escaping ≥ and ≤ #3444, Latex Output UTF8 #234

in case of utf8x option to inputenc, \DeclareUnicodeCharacter works with decimal, not hexadecimal Unicode code points. Further, it is not needed for handling U+00A0 as it does it automatically.

[jfbu]

MEMO 1: in fact with TeXLive 2016 it is not needed to make \DeclareUnicodeCharacter{00A0}{\nobreakspace } explicitely, because this is already done by utf8 option of inputenc package. (at least since 2016/02/28 v1.1s release of utf8enc.dfu, hence also in updated TeXLive 2015).

MEMO 2: for utf8x , it does it automatically first time it encounters the U+00A0 in document (at least on my locale which has utf8x.def 2004/10/17, and ucs 2013/05/11 v2.2.) Perhaps nevertheless I should add to the PR an explicit \\DeclareUnicodeCharacter{160}{\\nobreakspace} as it gains fraction of microsecond for latex build probably.

[tk0miya]

+0; I'm not good at utf8x package. so I have nothing to say.

[jfbu]

I have no experience myself with it. I know it was much in advance compared to LaTeX kernel, but now LaTeX kernel people have incorporated some of its ideas (in different ways) and people of influence on tex.sx do not seem to like it a lot. However in the case of #3444, I tested that utf8x could handle it without any need of additional preamble configuration. For this reason I will merge this if no objection within a week, thanks for reviewing !

[jfbu]

thanks for review @tk0miya now merging and will update CHANGES (for 1.5.4)