Bug#925116: posh: use memfd_create(2) for heredocs when available

[Clint Adams]

On Tue, Mar 19, 2019 at 05:52:05PM -0400, Daniel Kahn Gillmor wrote:

this appears to be done in the herein() function in exec.c.

Probably that should happen in io.c:maketemp() if TT_HEREDOC_EXP
is passed as the type.