[RFA/RFC Prec] Add process record skip 0/6

[Hui Zhu]

Hi guys,

Process record skip is a new feature of process record.  It let prec
record some functions of inferior as one instruction (record the
memory and reg that will be change in this function). It will make
prec speed up and use less memory than before.
The developer of gdb can add more function with
"record_skip_entry_create" (5 is the example).

When reverse exec the skip function, inferior will reverse exec to the
first address of record, this is because reverse exec handle the one
instruction function have something wrong, I have report it in
http://sourceware.org/ml/gdb/2009-08/msg00091.html

Please post your comments about it.

Thanks,
Hui