negative memory size in situations where the sprintf implementation of the
host system generated less decimal places than were requested.
Resolved this issue by making number_format examine the string returned
by spprintf and have it pad to the correct number of decimal places.
Added a test-case based on the bug report; the length of decimal places
required to trigger this bug is sprintf implementation dependent; as the
implementation is now using spprintf (provided by PHP), that number is
78 digits (NDIG - 2).
# I played with the idea of enhancing sprintf to do the equivalent, but
# it was too much effort considering that the precision of floats/doubles
# is not good enough to warrant it.
# This fix could do with some QA from someone else to make sure there are
# no memory bounds problems and then MFH it to PHP_4_3
