portable construction of relative include path from absolute filename
portable construction of relative include path from absolute filename

attempts to fixes broken windows build
geektoni/shogun,lambday/shogun,lambday/shogun,geektoni/shogun,geektoni/shogun,sorig/shogun,geektoni/shogun,geektoni/shogun,shogun-toolbox/shogun,lisitsyn/shogun,shogun-toolbox/shogun,karlnapf/shogun,sorig/shogun,sorig/shogun,besser82/shogun,karlnapf/shogun,karlnapf/shogun,besser82/shogun,lambday/shogun,karlnapf/shogun,shogun-toolbox/shogun,lisitsyn/shogun,shogun-toolbox/shogun,lisitsyn/shogun,karlnapf/shogun,sorig/shogun,lisitsyn/shogun,lisitsyn/shogun,sorig/shogun,besser82/shogun,lisitsyn/shogun,lambday/shogun,karlnapf/shogun,shogun-toolbox/shogun,sorig/shogun,geektoni/shogun,lambday/shogun,shogun-toolbox/shogun,lambday/shogun,besser82/shogun,besser82/shogun,besser82/shogun