Open options to control permissions on output streams

[kenbowen]

Design and implement an open option for output streams which can control the permissions attached to a (new) file opened as the target of a stream. It should be portable across the OSs we support, perhaps a minimalistic “executable” vs “non-executable”. The default for open(, write, …) should be “non-executable”.

[chuckhoupt]

It is odd that bsio.c calls Posix open() with the mode 0777 (which creates executable files). The mode 0666 would be more typical, and it would match ANSI fopen() behavior.

Maybe a bug-issue/fix could be created/commited for changing 0777 to 0666? Then this issue would be a further enhancement to add permission support (open, chmod, etc).

[kenbowen]

Default behavior to be taken care of by #144.