perf tools: Make perf able to read files from older ABIs

This patches provides a way to handle legacy perf.data
files.  Legacy files are those using the older PERFFILE
signature.

For those, it is still necessary to detect endianness but
without comparing their header->attr_size with the
tool's own version as it may be different. Instead, we use
a reference table for all known sizes from the legacy era.

We try all the combinations for sizes and endianness. If we find
a match, we proceed, otherwise we return: "incompatible file
format".

This is also done for the pipe-mode file format.

Signed-off-by: Stephane Eranian <eranian@google.com>
Cc: peterz@infradead.org
Cc: acme@redhat.com
Cc: robert.richter@amd.com
Cc: ming.m.lin@intel.com
Cc: andi@firstfloor.org
Cc: asharma@fb.com
Cc: ravitillo@lbl.gov
Cc: vweaver1@eecs.utk.edu
Cc: khandual@linux.vnet.ibm.com
Cc: dsahern@gmail.com
Link: http://lkml.kernel.org/r/1328826068-11713-19-git-send-email-eranian@google.com


Signed-off-by: Ingo Molnar <mingo@elte.hu>