ensure that is_symbol_table is set
v2.05

  - ensure that is_symbol_table is set when adding file to an
    archive.  This fixes a intermitent bug introduced in 2.04
AIX detection
start of a AIX BIG read

This needs to be refactored, in particular first and next should
be unified to avoid code duplication.  Also if the member table
is not at the end the way it is structured won't work correctly.
some todos