* Add Faddeeva functions for erfcx

* Fix c_code

* call c_header_dirs in Elemwise

* Add Faddeeva functions for erfcx

* Call CLinkerObject.c_header_dirs for scalar Op in Elemwise

* Add c_header_dirs method to aesara.scalar.Composite

* Clean up comments

* Remove Faddeeva.h
Co-authored-by: Brandon T. Willard <brandonwillard@users.noreply.github.com>