Added a fallback for  returning no NODE_CFLAGS (in node-0.6).
Added a fallback for  returning no NODE_CFLAGS (in node-0.6).

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