Building agent on Windows requires afxres.h, winres.h

afxres.h and winres.h are part of MFC and are not included in Microsoft Platform SDK. To build Zabbix agent on Windows users must either use non express edition of Visual Studio or copy the required files to Platform SDK installation. As we are not using MFC we should be able to replace afxres.h includes in resource.rc with winresrc.h allowing to build Zabbix agent with Platform SDK without any additional requirements.