b=865241 test HRTF panner left/right symmetry and block-offset invariance

--HG--
extra : transplant_source : Z%7E%83XS%0Ck%09%00%0A%CA%D9%FF%B8%D3%9E%FB%D72j
b=973782 revert 8e574d7a951a, intermittently failing test from bug 938022 DONTBUILD