Positional sub-categories not applied yet.

The spec wrongly has "H" where "HN" is meant.

Grammar from the spec!

Based on https://bugzilla.mozilla.org/show_bug.cgi?id=1183209

https://bugs.freedesktop.org/show_bug.cgi?id=91228

Commit cdcdfe61 changed two `#pragma
message` to `#pragma error` in hb-unicode.cc, however MSVC uses #error,
just like the #else branch. `#pragma error` is an unknown pragma so
MSVC does not fail the build because of it, which I believe was the
intention of that commit.

If it's meant to be an #error, then the #ifdef for _MSC_VER can be
removed entirely.

Fixes test-shape, and:
https://code.google.com/p/chromium/issues/detail?id=497578

Separate the loops for the two cases of replacing with space
and deleting.  For deleting, use the out-buffer machinery.

Needed for upcoming cluster merge fix.

Part of https://github.com/behdad/harfbuzz/issues/91

https://bugzilla.mozilla.org/show_bug.cgi?id=1167119

Based on data from http://upstream-tracker.org/versions/harfbuzz.html
Resolves #103

Applying unary minus operator to unsigned int causes the following
warning on MSVS:

  warning C4146: unary minus operator applied to unsigned type, result still unsigned

Based on patch from Koji Ishi.

Fixes https://github.com/behdad/harfbuzz/pull/110

Using latest gobject-introspection, I don't seem to be having this
problem anymore:

  https://bugzilla.gnome.org/show_bug.cgi?id=707656

Removing that kludge makes language_t behave more like the way I expect it
in Python.

Also fixes:
https://github.com/behdad/harfbuzz/issues/91

Fixes user_data_t

Apparently the code is already standardized:
https://www.microsoft.com/typography/otspec/languagetags.htm

Very anaemic, needs to descripe the format understood by
hb_feature_from_string() etc., but it is just start.

The code is not standardized yet, but is used in some Google fonts.

Fixes https://code.google.com/p/chromium/issues/detail?id=476913

This reverts commit 89cbd4d9.

See discussion:
https://bugzilla.gnome.org/show_bug.cgi?id=747772

Not sure we have any right now; motivated by this:
https://bugzilla.gnome.org/show_bug.cgi?id=747772

Annotate the output parameter.

It should not be freed by the caller.

Based on patch from Björn Breitmeyer

Previously, when creating an object from inert inputs (eg:
"hb_font_create(hb_face_get_empty())") we returned the inert
empty object.  This is not helpful as there are legitimate
usecases to do that.

We now never return the inert object unless allocation failed.

Tests are revised to reflect.