hdf5_ep

[svn-r9861] Purpose:
    Bug fix

Description:
    Add detect vasprintf() routine and use it instead of vsnprintf() when
formatting error descriptions if it's available.

    Added configure test to detect "broken" vsnprintf() implementations which
don't return the correct number of character for strings that are too long to
fit into the buffer provided (currently a problem on the SGIs and probably the
HP).

    Re-wrote error formatting code in H5Epush_stack() to handle broken
vsnprintf() implementations, etc.

Platforms tested:
    IRIX64 6.5 (modi4)
    h5committest