Fix a segmentation fault.

Child modifications should come before possible deletion of the child...

Error found by Haiyan when running scram.
using hash table to de-duplicate namelist
add stderr redirection to system function
move special caller checking procedure from pfs_package_create.c into pfs_table.cc
add -Wall -pg into configure
hardcode copy degree
modify comments about special_caller
check the state of namelist_table instread of namelist_file