giscanner: slighlty more efficient identifier parsing
giscanner: make DocAnnotations an odict subclass
giscanner: use SqlAlchemy's OrderedDict implementation

g-ir-scanner can be a bit on the slow side. While true we
now do a bit more work parsing GTK-Doc comment blocks, one
of the biggest slow-downs comes from the OrderedDict
implementations we have been using.

Time needed to build Gtk-3.0.gir:

1) The original DictMixin sublass:
     92,79867 seconds
2) Python's collections.OrderedDict class:
     88,65786 seconds
3) Larosa/Foord implementations from http://www.voidspace.org.uk/python/odict.html :
     71,64323 seconds
4) SqlAlchemy's implementation:
     66,12449 seconds

Looks like we have a clear winner with the SqlAclchemy
implementation. Additionally there is less complexity
pollution in the profiles (I recommend looking at
them with http://pypi.python.org/pypi/RunSnakeRun).
giscanner: store indentation of GTK-Doc comment blocks

so we can rewrite them in source files without destroying
the indentation before the "*".
giscanner: emit 'incorrect number of parameters in comment block' warning

instead of silently ignoring parameter names on signals when the
number of parameters doesn't match our expectations.
giscanner: make _pass_fixup_hidden_fields() more readable
giscanner: make _pass_read_annotations2() more readable
[WIP] Add tool fixing GTK-Doc comment blocks in .c and .h files

Just a standalone script for now, should probably eventually
go into g-ir-annotation-tool...
[WIP] TODO: document what's left to do on this (annotationparser fixes) branch
[WIP] docs: improve layout
!!! for testing only !!!
Work in progress...