Add check for interface calls using spaces instead of commas

[dburgener]

For example:

foo(bar baz)

If foo expands to something like:

allow $1 $2:file perms;

Then "bar baz" is substituted as $1, and $2 is the empty string and everything works fine. But obviously strange errors could occur if later the interface is modified to separate $1 and $2.

[dburgener]

Added in 9fc3c50