Don't include <errno.h> in reloc_elf.c, as it includes <stand.h> just
after it, which has a conflicting definition of errno. This leads to
the following warning with clang 4.0.0:
In file included from sys/boot/common/reloc_elf32.c:6:
In file included from sys/boot/common/reloc_elf.c:37:
/usr/obj/usr/src/tmp/usr/include/stand.h:155:12: error: this function declaration is not a prototype [-Werror,-Wstrict-prototypes]
extern int errno;
^
sys/sys/errno.h:46:26: note: expanded from macro 'errno'
#define errno (* __error())
^MFC after: 3 days