Log Message:
Update to 5.21p:

                        CHANGES IN VERSION 5.21p
                 (Klaus Reimer <k@ailis.de>, 07 Aug 2010)

Replaced mktemp with mkstemp.
Set correct version number and updated creation date in command-line help.
Corrected content of PATCHLEVEL file.
Added man page for marc.
Added install make target.
Added -Wall compiler flag.