gen_stream test suite fix for spurious process count failure

[jay@REDACTED]

I changed the test suite for gen_stream to not rely on
erlang:system_info(process_count).  Instead I exposed the processes using
a new interface and check the actual number processes returned by the
gen_stream server.


git fetch git://github.com/jaynel/otp.git gen_stream-test-track-procs


I hope this works.  I pulled a recent dev, then got jn/gen_stream and
applied it as a patch on top of my dev.  My new changes plus the patch are
all bundled into this single commit.

I only changed two files:
   lib/stdlib/src/gen_stream.erl
   lib/stdlib/test/gen_stream.erl

If you have any trouble, just cherry pick these two files and apply them
on top of jn/gen_stream in pu.

This fixes the spurious random failures.  It does not attempt to address
the failure caused in the shell test suite.  I think I know how to track
that one down and hope to get to it in the next few days.

jay