lazy evaluation A* condition

if the first condition is met, no need to iterate the node list
Weight of diagonal nodes in A* algorithm

Diagonal nodes account for a slightly longer distance than an adjacent
node so calculate the distance correctly. Its already done like this in
the other branch of the same if statement.
Allow skipping cutscene
Merge pull request #661 from igorko/master

Allow skipping cutscene
Set proper limit for path finding

The exploration limit for path finding was lowered to some guess
depending on the screen size.

Also the hardcoded 1000 in Avatar was removed.

This fixes #658.
Remove obsolete PATH_MAX_TILES definition
MapCollision:compute_path set the default limit parameter to 0

We're dealing with unsigned data types, so better not have -1.
Merge pull request #78 from stefanbeller/pathfinding_performance

merge intelligent pathfinding limit
Target closest node when pathfinding fails

If pathfinding fails to find the destination, target the closest node
that was reached instead.
Fix inconsistency with checking diagonal distance
comment
Animation: Move implementation to cpp file
Introduce file SharedIncludes which includes all common include files

Having this patch applied leads to these timings:
$ time make
real	0m14.372s
user	1m26.200s
sys	0m8.460s

Before I had:
real	0m14.970s
user	1m25.736s
sys	0m9.140s
Remove <iostream> includes as it's covered by shared includes
Move SDL includes to shared includes
Rename SharedIncludes to CommonIncludes
Remove any other occurences of <string> includes
Move <sstream> to CommonIncludes
Sort include lists alphabetically

Also always put the includes (#include "file.h") of flare before
generic includes (#include <file>)

Signed-off-by: Stefan Beller <stefanbeller@googlemail.com>
Remove as many #includes by forward declarations in headers