review erfcx(Inf) and cerfcx(Inf)
In realtest.c, this line is currently disabled:
// iTest(&result, "erfcx", cerfcx, erfcx);
Otherwise we get a failure under Debian:
5/6 Test #3: realtest .........................***Failed 0.08 sec
failure in subtest 120010: erfcx(Inf)
- fct value 0
- expected -nan
=> error inf above limit 1e-13
1/142515 tests failed