CORE-12686 This collection of libraries consist in: - a down-level `pathcch_static` PathCch library, to be used for programs that need to run on Windows 7 and below; - Windows 8+ compatible libraries importing from either kernelbase.dll (`pathcch_kernelbase`), or from the corresponding APISET api-ms-win-core-path-l1-1-0.dll (`pathcch`, which is Win8+ PSDK compatible). The down-level static library is compiled by reusing the newly-introduced kernelbase's path.c, instead of using a specific pathcch.c. Unrelated functions are excluded from compilation by putting them into `#ifndef STATIC_PATHCCH ..... #endif` blocks.