Replace the function "mktemp" by "mkstemp"

[elfring]

A message like the following can be displayed during the software build process.

warning: the use of `mktemp' is dangerous, better use `mkstemp'

This open issue can be fixed in the following ways.

• Richard Atterer (2001-07-03)
• Markus Elfring (2011-02-10)

[ChrisDodd]

The proposed solutions just silence the warning and do nothing to fix the underlying security hole (which is casued by the fact that these files are closed then reopened for reading later in the program.)