consolidate BINPRM_FLAGS_ENFORCE_NONDUMP handling

new helper: would_dump(bprm, file).  Checks if we are allowed to
read the file and if we are not - sets ENFORCE_NODUMP.  Exported,
used in places that previously open-coded the same logics.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --cc fs/binfmt_elf.c
Simple merge

diff --cc fs/binfmt_elf_fdpic.c
Simple merge

diff --cc fs/binfmt_misc.c
Simple merge

diff --cc fs/exec.c
Simple merge

diff --cc include/linux/binfmts.h
Simple merge