ext:run-program's :environ keyword difficult to use and with inconsistent behaviour.

These are really two issues but I'll discuss them both here.

1. The snippet

(ext:run-program "/usr/bin/env" nil :output t :environ (list "A=b"))

fails to run because "A=b" is not of type base-string. One needs to use something like this:

(ext:run-program "/usr/bin/env" nil :output t :environ (list (coerce "A=b" 'base-string)))

2. The behaviour of

(ext:run-program "/usr/bin/env" nil :output t :environ nil)

compared to

(ext:run-program "/usr/bin/env" nil :output t :environ (list (coerce "A=b" 'base-string)))

is inconsistent: In one case, the default case is kept as-is. In the other, rather than having "A=b" appended to it (discarding any previous assignment to A), the environment is completely replaced with the singleton ("A=b"); in particular, PATH is gone.

proposed solution: coerce environ to base-string if it's a string in run-program, default argument to :default and nil creates empty environment.

Added feature non-urgent project support labels

changed milestone to %ECL 16.2.0