conform/linknamespace: whitelist matherrf/matherrl

glibc supports the deprecated matherr hook for math error reporting.  The
conform tests take this into consideration and whitelist this symbol when
running linknamespace tests.

The ia64 libm code has long provided two additional hooks in this space:
	matherrf (for floats)
	matherrl (for long doubles)

Which causes the conform tests to fail with chains that all look like:
	[initial] __atan2 ->
	[libm.a(e_atan2.o)] __libm_error_support ->
	[libm.a(libm_error.o)] matherrf

We can't (losslessly) redirect existing usage of these funcs to matherr
because the structure passed in is different -- matherr uses a struct with
doubles while matherrf/matherrl use floats and long doubles respectively.
Plus, this has been part of the exported ABI since glibc-2.2.3, so it
doesn't feel right to change it so late.

Until we get around to obsoleting matherr entirely, whitelist these two
additional ia64 symbols.