Basic timing of programs in PHCv2.3

The files in this directory were already part of the very early releases
of PHCpack, but were moved to a separate subdirectory of System to avoid
the copying of "win_timing_package" to "timing_package" for an often more
common Windows installation, which uses the basic timer facilities.

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file name                 : short description
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get_clock.c               : calls the C routine "clock"
get_clocks_per_sec.c      : returns the constant CLOCKS_PER_SEC from time.h 
timing_package            : measures usage of computing resources
ts_timer                  : timing of summation of natural numbers
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The get_clock.c tends to return a 32-bit number which causes overflow.
