[PATCH 0/2] Add a new warning option -Wstrict-flex-array

[Qing Zhao <qing.zhao@oracle.com>]

This patch serie include two changes:
  1. Change the name of array_at_struct_end_p to array_ref_flexible_size_p.
  2. Add a new warning option -Wstrict-flex-arrays and at the same time
keep -Warray-bounds unchanged from -fstrict-flex-arrays.

The new warning -Wstrict-flex-arrays is implemented at the same place as 
-Warray-bounds. Since we need to keep the old behaviors of
-Warray-bounds=[1|2], we refactor the routine
"array_bounds_checker::check_array_ref" to make it work for both
-Warray-bounds and -Wstrict-flex-arrays.  

if -Warray-bounds, -Wstrict-flex-arrays, -fstrict-flex-arrays presents
at the same time:
  A. -Warray-bounds will be not controlled by -fstrict-flex-arrays;
  B. -Wstrict-flex-arrays will be controled by -fstrict-flex-arrays;
  C. both -Warray-bounds and -Wstrict-flex-arrays will report warnings
     according to it's own rules.

bootstrapped and regression tested on both x86 and aarch64. no issue.
Okay for commit?

thanks.

Qing