Use xmlStrlen instead of strlen for better compatibility
Use xmlStrlen instead of strlen for better compatibility

closes gh-10

Visya/libxmljs,Visya/libxmljs,gagern/libxmljs,libxmljs/libxmljs,CodeFridge/libxmljs_mem,Konsus/libxml,hildjj/libxmljs,polotek/libxmljs,improvisio-software/libxmljs,rc0x03/libxmljs,gagern/libxmljs,rchipka/libxmljs,apeace/libxmljs,sergeche/libxmljs,hildjj/libxmljs,rchipka/libxmljs,Visya/libxmljs,isaacs/libxmljs,isaacs/libxmljs,apeace/libxmljs,gagern/libxmljs,CodeFridge/libxmljs_mem,libxmljs/libxmljs,isaacs/libxmljs,rchipka/libxmljs,isaacs/libxmljs,polotek/libxmljs,polotek/libxmljs,sergeche/libxmljs,CodeFridge/libxmljs_mem,improvisio-software/libxmljs,Konsus/libxml,libxmljs/libxmljs,rc0x03/libxmljs,improvisio-software/libxmljs,rc0x03/libxmljs,Konsus/libxml,sergeche/libxmljs,hildjj/libxmljs