• pkg_add spawns itself as argv[0] when installing dependent packages, to enable the use as a port on older systems

• use absolute paths in all calls to external programs, to account for strange PATH settings

• use INDEX or INDEX-5 depending on FreeBSD version, to enable the use on FreeBSD 4.x as a port.

• conditionalize all 4.x/5.x differences on __FreeBSD_version, so that the pkg_install tools can be kept in sync on 4.x and 5.x

• Bump PKG_INSTALL_VERSION

Reviewed by: portmgr (bento run)
MFC after: 4 weeks