Add expr_callee_abi

[Jeff Law]

On 10/11/19 8:39 AM, Richard Sandiford wrote:
> This turned out to be useful for the SVE PCS support, and is a natural
> tree-level analogue of insn_callee_abi.
> 
> Tested on aarch64-linux-gnu and x86_64-linux-gnu.  OK to install?
> 
> Richard
> 
> 
> 2019-10-11  Richard Sandiford  <richard.sandiford@arm.com>
> 
> gcc/
> 	* function-abi.h (expr_callee_abi): Declare.
> 	* function-abi.cc (expr_callee_abi): New function.
OK.  Yes I realize you're not using it on the trunk yet :-)

jeff