Update uconv.patch to exactly match upstream SVN r37045.

Update uconv.patch to exactly match upstream SVN r37045.

This patch was sent upstream and modified before landing there. This CL
reverse-applies uconv.patch, updates uconv.patch with a copy of SVN
r37045, and re-applies the new patch.

Notable changes include:
- Renaming UCONFIG_NO_NON_HTML5_CONVERSION to
  UCONFIG_ONLY_HTML_CONVERSION.
- Removing a few UCONFIG_ONLY_HTML_CONVERSION guards.
- Fixing some unused variable warnings.
- Cleaning up some comments.

BUG=506434

[Matt Giuca, 2015-07-02 03:32:05]

mgiuca@chromium.org changed reviewers:
+ jshin@chromium.org

[Matt Giuca, 2015-07-02 03:32:06]

See description on bug.

Not urgent (I will disable Clang warnings on this library in the mean time).
Maybe instead of doing this, you could just update to ICU 55 if that's something
you were going to do anyway.

Also, who are the owners for this code? I don't see an OWNERS file.

[jungshik at Google, 2015-07-08 00:15:34]

On 2015/07/02 03:32:06, Matt Giuca wrote:
> See description on bug.
> 
> Not urgent (I will disable Clang warnings on this library in the mean time).
> Maybe instead of doing this, you could just update to ICU 55 if that's
something
> you were going to do anyway.
> 
> Also, who are the owners for this code? I don't see an OWNERS file.

Yes, I'm going to upgrade to ICU 55 pretty soon. Adding a patch this big for ICU
54 is not worth the effort. 

Thank you for the CL, anyway.

[Matt Giuca, 2015-07-08 01:57:25]

OK.