refactor pool_calc_duchanges a bit
refactor pool_calc_duchanges a bit

No functual changes.

jsilhan/libsolv,JacksonIsaac/libsolv,jsilhan/libsolv,jsilhan/libsolv,JacksonIsaac/libsolv,jsilhan/libsolv,jsilhan/libsolv,JacksonIsaac/libsolv,JacksonIsaac/libsolv,jsilhan/libsolv,JacksonIsaac/libsolv