lr_register.
(rs6000_in_function_epilogue_p): Check for bctr.
(skip_prologue): Initialize lr_register. Set lr_reg to a register
number. Set gpr_mask and used_bl. Continue scanning while some
expected registers are not saved. Set lr_register if LR is not
stored.
(rs6000_frame_cache): Handle gpr_mask and lr_register.
* gdb.arch/powerpc-prologue.exp: Correct saved registers.