spawn: use glibc style to keep differences down

spawn: use glibc style to keep differences down

There's no point in reformatting the code style when we're sourcing
most of it from glibc.  Further, the changed style breaks with older
compilers, and pollutes the namespace with non-double leading under-
scores.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>