Updated 'preemph.c' and 'q_pulse.c'

On host toolchains, __unused doesnt seem to be present. Hence
updated all instances in 'q_pulse.c' to use
__attribute__((unused)) instead.

For host toolchains, stdint.h needs to be added in 'preemph.c' so
that INT32_MAX is correctly defined

Test: Build libstagefright_amrwbenc
Bug: 170360841

Change-Id: I4ad6fa070b6b4d6b016e1c47ffbc9eb1c4130390