libm: Factor out common expected symbol list.Should substantially reduce the maintenance burden.
libm: Do the weak alias dance for asin, acos, atan.These are used internally by the complex trig functions, so they needweak aliases.
libm: Do the weak alias dance for sin/cos/tan/finite{,f}.tan isn't used internally, but it's confusing for it to be treateddifferently from sin and cos, and there's no harm in doing the danceunnecessarily.
libm: Memorialize expected symbols on various architectures.This will reduce the risk of accidentally adding or deleting thewrong symbols while fixing the aliases.(This is all the architectures I have a build tree for handy; can addother architectures like m68k later.)