eliminate feature tests from lo-specfun.h * lo-specfun.h, lo-specfun.cc (xacosh, xasinh, xatanh, xerf, xerfc xexpm1, xlog1p, xcbrt): Rename to have 'x' prefix. Conditionally define in .cc file. Change all uses Move complex versions of acosh, asinh, and atanh functions here.