giscanner: add AnnotationParser tests

The tests in giscanner/annotationpatters.py only test the regular
expression programs used when parsing GTK-Doc comment blocks but
do not test the structure of the resulting "parse tree".

This patch adds 193 GTK-Doc comment blocks and the expected
results AnnotationParser should return (with it's current level
of understanding of GTK-Doc comment block syntax). These are
compared by tests/scanner/annotationparser/test_parser.py which
complains with a diff on failure.
giscanner: move unittests from giscanner/annotationpatters.py...

... to tests/scanner/annotationparser/test_patterns.py
giscanner: construct list of possible tag names for TAG_RE from _ALL_TAGS...

... instead of having a secondary hard-coded list. This results
in the removal of giscanner/annotationpatterns.py to prevent a
circular import.
giscanner: treat the GTK-Doc Description: tag like any other tag

and add paragraph break tests.
giscanner: Correctly detect invalid GTK-Doc comment block end markers
giscanner: remove re.MULTILINE usage from annotationparser

These are remnants from the original prototype and are no
longer used.
giscanner: update annotationparser to most recent gtkdoc-mkdb bug fixes.

This patch adds a test for and implements a more generic solution to
GTK-Doc commit 47abcd53b8489ebceec9e394676512a181c1f1f6
Update GLib annotations to master

Which at the time of writing is GLib commit 08cfcdc81add6f6f2247b1cc82d2c15ad27001f0
giscanner: fix DocBlock().comment

If there is no comment block description, DocBlock().comment
should be None. This results in the removal of unneeded blank
lines in the output of DocBlock().to_gtk_doc and hence the .c
files generated by misc/update-glib-annotations.py
giscanner: don't continue parsing after muliline descriptions
giscanner: deprecate top level g-i specific GTK-Doc tags.

Rationale
---------

The first wave of improvements on AnnotationParser intended
to fix bug http://bugzilla.gnome.org/show_bug.cgi?id=672254
(multiline descriptions on tags not working correctly, polluting
the comment block description instead) had an unforseen side
effect reported in bug http://bugzilla.gnome.org/show_bug.cgi?id=674658.

Analysing this problem we found that even though comment blocks
having g-i specific tags before the comment block description
are technically malformed, g-i specific tags never have a multiline
description to begin with (but the basic set of GTK-Doc tags do).
During this analysis, a secondary bug report
(http://bugzilla.gnome.org/show_bug.cgi?id=676133) was filed with
the GTK-Doc project because it was found that the same malformed
comment blocks did not result in the expected html output.
All hell broke loose...

In short, we learned that these g-i specific top level tags should
never have existed in the first place, preferring annotations on the
identifier instead. As a result, this patch deprecates g-i specific
top level tags and implements them as annotations on the identifier
instead. Without breaking support for malformed comment blocks still
using g-i specific top level tags.

This means that all annotated code "out there" should continue to work
just fine with this version of g-i, but when a developer decides to
fix deprecation warnings in his/her comment blocks, the dependency
on g-i needs to be raised to a version that contains this patch.

Overview of changes
-------------------

1) giscanner/annotationparser.py and giscanner/maintransformer.py
   have been adjusted to deprecate g-i specific top level tags
   and now implement these in terms of annotations on the identifier.
   The Attributes: tag and it's new (attributes) annotation
   counterpart continue to be broken (regression introduced in
   commit 182fdfec261f36fa095484352b9b834861036907), which will be
   addressed in a followup patch.

2) AnnotationParser().parse_options() has learned to correctly parse
   multiple closing parentheses, which is for example required for the
   new syntax in tests/scanner/annotationparser/gi/annotation_type.xml:
   * AnnotationObject:hash-table: (type GLib.HashTable(utf8,gint8))

3) comment blocks in tests/*.c and tests/*.h had to be adjusted as
   tests are not allowed to emit warnings. As a result, these test
   cases now no longer use g-i specific top level tags but annotations
   on the identifier instead.

This hopefully satisfies https://bugzilla.gnome.org/show_bug.cgi?id=676133
while fixing http://bugzilla.gnome.org/show_bug.cgi?id=674658 as a side effect.
giscanner: Fix annotations pattern

The "annotations" part of our regular expression programs failed
on multiple closing parentheses like (element-type GLib.List(utf8)).
This patch adds tests and fixes the issue.

Thanks to Colin Walters for the scrutiny and voicing his concerns on irc!