Create engrampa.appdata.xml

An appdata file for inclusion in the upcoming software centers as per the new freedesktop.org specs.

It should be placed in /usr/share/appdata/ similar to the way .desktop files are placed in /usr/share/applications/, e.g. if you have a "$(datadir)/applications" definition in your makefiles, you need to add a "$(datadir)/appdata" as well.

Please, skim through the file in case I made a mistake and please, include it in the 1.8 branch as well.

Thanks!
appdata: Add autotool bits for appdata
Fix make distcheck
appdata: Add necessary markers for translation
don't leak memory
Fixed crash when clicking Cancel in Add Files

This reworks the patch already taken from gnome bug 631472 as there
is more done in the commit that makes sense.

Taken from FR commit: 77e9b777042c557c961f058ecab2691a4fd19a62
From: Paolo Bacchilega <paobac@src.gnome.org>
Gnome bug: http://bugzilla.gnome.org/show_bug.cgi?id=631472
renamed some variables to make the code clearer

Taken from FR commit: f0cadcb012c7393aafb056a01260f997ee23e93a
From: Paolo Bacchilega <paobac@src.gnome.org>

Picked this up as it makes it easier to use more code in the future.
fixed thel macro name

Taken from FR commit: 7ab015e3b96b0b8df33dd30d54216ee202a1c5e9
From: Paolo Bacchilega <paobac@src.gnome.org>
use g_get_user_config_dir instead of using .config/mate

Also provide an automatic migration mechanism.

Based on FR commit: 7fd220a834f16b260da8f5ddc1250c43b9dbefd8
From: Paolo Bacchilega <paobac@src.gnome.org>
use the provided action instead of always using CREATE_NEW_ARCHIVE

Based on FR commit: 82ab7cefc04a1313acf77cb8662fc1e32ccc0a52
From: Paolo Bacchilega <paobac@src.gnome.org>
do not expand the extra widget in the 'new' dialog

Based on FR commit: 02e93b44321f6c9bdad5af1a0d4d9251b8456242
From: Paolo Bacchilega <paobac@src.gnome.org>
Only use intltool
added focus stealing prevention code

Based on FR commit: 1a31dc3abbe42dcee6de79495bca0af1d69991cc
From: Paolo Bacchilega <paobac@src.gnome.org>
check for pkg-config before actually using it
Simplify and cleanup configure.ac a bit
require Gtk+ 3.0.2 for the primary-toolbar class
Gtk3: use gdk_display_get_app_launch_context instead of gdk_app_launch_context_new

Taken from FR commit: 02f2fa8dc6c41d04e105b02f662b23a2c910d6cb
From: Paolo Bacchilega <paobac@src.gnome.org>
do not set the "last output" dialog as modal to allow the user to resize it

Based on FR commit: b950fd5ac1be8d32734a13b2a87d95ade702256d
From: Paolo Bacchilega <paobac@src.gnome.org>
Prevent a NULL pointer deref in mktime_from_string().

It's possible to call mktime_from_string() with NULL arguments for day,
month and year. This would in turn lead to calling atoi(NULL), which
leads to a crash.

So instead fill in any NULL values with the corresponding unit from
Jan 1st 1970.

Based on FR commit: 2899c092f249a4fa822a896baf128b6c8c75b634
From: Jasper Lievisse Adriaanse <jasper@humppa.nl>
Pointer arithmetic fixes for end of string access

Based on FR commit: 3d7fa24ca267e333d7406eff38ec02b519110ecc
From: Iain Nicol <iainn@src.gnome.org>
Gnome bug: http://bugzilla.gnome.org/show_bug.cgi?id=651416