Export the static ELF and compressed kdump vmcoreinfo_read_string()
functions from netdump.c and kdump.c via a new read_vmcoreinfo()
method in the global program_context structure.  The function
get_log_from_vmcoreinfo() will access vmcoreinfo data via the
new pointer instead of requiring its callers to pass pointers to
their dumpfile-specific function.
(anderson@redhat.com)