Lower defaults in confdefs.h

[Joel Sherrill]

I have been mulling over lowering some of the default values
in confdefs.h to reduce executive workspace size.  In particular,
these default too high for most applications:

CONFIGURE_MAXIMUM_TASKS - Classic API tasks defaults to 10
CONFIGURE_MAXIMUM_POSIX_THREADS - POSIX threads defaults to
  10 when POSIX API is enabled
CONFIGURE_MAXIMUM_ITRON_TASKS - ITRON tasks defaults to
  10 when ITRON API is enabled
CONFIGURE_LIBIO_MAXIMUM_FILE_DESCRIPTORS is the number of
  file descriptors and defaults to 20.

Remember each task configured results in stack space
being reserved so 30 tasks can be a LOT of memory.
I think the defaults for tasks/threads should be 0 thus
forcing the application to specify an appropriate number.

I think the default number of file descriptors should
be 3 to support stdin, stdout, and stderr.

I am also open to discussion as to whether 
CONFIGURE_USE_MINIIMFS_AS_BASE_FILESYSTEM should be the default.
This reduces the functionality of the IMFS to be comparable
to the functionality in version 4.0 -- device nodes.

I bring this up now because if the defaults are to change it
should happen before a major release to avoid getting more
applications dependent on the higher defaults.

Comments appreciated.

-- 
Joel Sherrill, Ph.D.             Director of Research & Development
joel at OARcorp.com                 On-Line Applications Research
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