hdf5_der

[svn-r19879] Purpose:

    Improve portability of flushrefresh test.

Description:

    The flush/refresh API test was hanging on linew because 
    Solaris's 'date' tool does not recognize the "+%s" option,
    which returns time since the epoch on other UNIXes.

    There doesn't seem to be a good way to unify the tools,
    however, Perl can be easily used for this function. I've
    modified configure to always check for the existence of
    Perl (previously it only did so if GNU compilers were being
    used), and the flush/refresh test script now uses perl to
    perform this timestamping functionality rather than date,
    by default. (if Perl is not detected by configure, the
    script will use date as it did prior to this modification).

    Fixed a few other compatibility issues w/ Solaris in passing:
    - fixed 'head' and 'tail' parameters to be more portable
    - avoid passing NULL to an fprintf call in flushrefresh.c

Tested:

    - Tested testflushrefresh.sh on jam, linew, heiwa, liberty, 
      duty, ember, and abe.