Fix compilation errors, add customizability#4

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nabijaczleweli wants to merge 3 commits intobrofield:masterfrom

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Commits on Sep 14, 2015

Add include guards around SG_PATH_CHAR
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Commits on Sep 15, 2015

Fix compilation error, where all symbols used in WinAPI are not defined
nabijaczleweli
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Also include <mbstring.h> with _MBCS defined
nabijaczleweli
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