Merge pull request #188 from dalerank/master

mingw 4.8 support. new picture manager. VFS upgrade.
Use current directory as fallback application directory

With this more sane paths are generated, e.g. ./resources/foo instead
of /resources/foo
Fix bunch of 'deleting pointer to incomplete type' errors detected by clang

(without explicit class destructors, destructors of SharedPtr<Impl>
are generated with incomplete Impl type, causing UB. With explicit
destructors defined in .cpp file where Impl's are properly defined
this is fixed).

This change may be incomplete - I've fixed only classes clang
complained to.
Set warning and debug compiler flags for clang as well as gcc

-Wno-unused-value is useful to hide warnings on sizeof()'s used in static asserts
Merge pull request #192 from AMDmi3/clang-fix

Fix UB on GuiInfoBox-derived objects destruction and improve clang support
Merge pull request #191 from AMDmi3/master

Use current directory as fallback application directory
Merge branch 'master' of https://github.com/gecube/opencaesar3

Conflicts:
	oc3_gui_info_box.hpp