Script passed as pipe, fix for locks, support for python

[fabio-brugnara]

This PR proposes a solution (at least in my experience), for a couple of questions appearing among the Issues.

1. Remove the limitations of command line length limits and exposability by using pipes instead of command line to pass the script to the interpreter. A -P option is added to enable this.
2. Remove occasional locks introduced by a race condition in the untraceable() function: the possibility that the CONT signal arrives before the process has actually entered the stopped state, being therefore discarded.
3. Add support for python script.

A drawback of the "pipe" feature, is the fact that the script may lose the possibility to retrieve the original name by accessing $0. Often this can be worked around referring to the $_ environment variable, but not always. In exchange for this annoyance, the limit on the script size and the possibility of seeing the source in clear with ps or /proc/*/cmdline both disappear.

These modifications have been applied to the version found in Francisco Rosales' page and have been working reliably for years under linux.

[neurobin]

Please initialize to 0

[fabio-brugnara]

OK, but static variables are initialized to 0 anyway

[fabio-brugnara]

I'll do, but if you feel it is necessary to modify something, you should have push access to my fork.
However, if you prefer to ask me to operate on it, no problem at all.