Sync test-string.h with glibc

This patch syncs test-string.h with latest glibc (commit a502c5294b4)
code. The only difference is the use of CMDLINE_PROCESS macro because
of test-skeleton.c.

It also removes the ununsed file hp-timing.h (since cortex-strings does
use the glibc benchtests code).

Change-Id: I213293fa0861a616086b190fc88d52c2f9654bc9
13 files changed