tests: prevent warnings with some make implementations

some make implementations don't like empty $(AM_V_GEN) rule
commands, see http://lists.gnu.org/archive/html/bug-coreutils/2009-04/msg00251.html
for more info.
build: use AC_LINK_IFELSE instead of AC_TRY_LINK

AC_TRY_LINK is obsolete...
build: prevent warnings during dist/distcheck

Make transforms tr '/' '\\' into tr '/' '\', leading to
tr: warning: an unescaped backslash at end of string is not portable
so double escape to make the warnings go away...
tests: interesting annotationparser test case

GTK-Doc has trouble parsing multiline parameter
description fields if the first word of a continuation
line is "returns". We're already doing the right thing
but make sure we continue to do so in the future

https://bugzilla.gnome.org/show_bug.cgi?id=708445
update .gitignore
[WIP] Add a tool fixing GTK-Doc comment blocks in .c and .h files

Just a standalone script for now, should probably eventually
go into g-ir-doctool or g-ir-annotation-tool...
[WIP] giscanner: include linemarkers in "gir/[gio|glib|gobject]-2.0.c"

Makes it obvious where a GTK-Doc comment block was picked up.

Note that these are not C pre-processor style linemarkers on
purpose to prevent g-ir-scanner's SourceScanner() from tripping
up over the non-absolute paths in the generated
"gir/[gio|glib|gobject]-2.0.c" files.
[wip]: gir xml schema

reset && time find /home/dieterv/gnome.org/checkout/gobject-introspection/gir/ /home/dieterv/gnome.org/prefix/share/gir-1.0/  -name "*.gir" -exec xmllint --noout --nonet --schema /home/dieterv/gnome.org/checkout/gobject-introspection/giscanner/gir/gir.xsd '{}' \;
!!! for testing only !!!