PR22245, Fix potential UB in bfd_set_error

PR22245, Fix potential UB in bfd_set_error

Passing enum as a first argument to variadic argument function
may lead to undefined behavior. The explanation on CERT site:
https://www.securecoding.cert.org/confluence/display/cplusplus/
EXP58-CPP.+Pass+an+object+of+the+correct+type+to+va_start

The bug was found by Kirill Nedostoev (nedostoev.ka@phystech.edu)
when he tried to build GNU binutils with Clang 7.

	PR 22245
	* bfd.c (bfd_set_error): Avoid UB on passing arg to va_start that
	undergoes default promotion.
	* bfd-in2.h: Regenerate.