Tweak Some Unicode-Related Text

[RexJaeschke]

Recently, I started writing a formal spec for the V11 feature, UTF-8 string literals. However, as I was reading the Draft V8 Ecma C# spec, it became clear to me that it didn’t say enough and/or wasn’t as clear as it could be w.r.t the (presumed) current intention regarding Unicode support. So, before I go back to writing that V11 feature spec, I created this PR, which contains a set of proposed improvements to the current Ecma spec. Basically, I want a better base on which to add the V11 (and possibly later) extensions. This PR includes the following kinds of edits:

1. Use grammar rule name instead of the descriptive English equivalent.
2. Use string instead of "string," as we'll have different kinds of string once UTF-8 support is added.
3. Use char instead of "character" where that makes it more precise.
4. Remove duplication of normative text (w.r.t conformance).
5. Use terms consistently.

I don't expect this to be controversial. The only new normative text has to do with explicitly saying that type string uses UTF-16 encoding.

@jskeet I added you as a reviewer, as I know you have written about some Unicode issues. @KalleOlaviNiemitalo If you have expertise in this area, I'd appreciate your feedback.

[RexJaeschke]

Regarding endianness, if I remove the normative text (and the corresponding entry in the Portability-issues annex) re that, will that resolve most objections to my proposed edits? if so, hopefully we can wrap this up on the next call.

[jskeet]

Regarding endianness, if I remove the normative text (and the corresponding entry in the Portability-issues annex) re that, will that resolve most objections to my proposed edits? if so, hopefully we can wrap this up on the next call.

I think I'd need to rereview to get myself back into context, but it would at least be a step in the right direction. (And we have some time before the next call, to do any more back and forth.)

[jskeet]

Rex: any chance you'd be able to remove the normative endianness aspects before the meeting? (We may not be able to merge, but it would be easier to discuss.)