SCP: Generalized DATE and TIME variable insertion adding support for ISO 8601 date values. Inspired by Christian Gauger-Cosgrove.

ISO 8601 support without requiring C99 strftime functionality.

          %DATE%                yyyy-mm-dd
          %TIME%                 hh:mm:ss
          %DATETIME%       yyyy-mm-ddThh:mm:ss
          %LDATE%               mm/dd/yy (Locale Formatted)
          %LTIME%               hh:mm:ss am/pm (Locale Formatted)
          %CTIME%               Www Mmm dd hh:mm:ss yyyy (Locale Formatted)
          %DATE_YYYY%     yyyy              (0000-9999)
          %DATE_YY%          yy                  (00-99)
          %DATE_MM%       mm               (01-12)
          %DATE_DD%         dd                  (01-31)
          %DATE_WW%       ww                 (01-53)     ISO 8601 week number
          %DATE_WYYYY%  yyyy              (0000-9999) ISO 8601 week year number
          %DATE_D%            d                    (1-7)       ISO 8601 day of week
          %DATE_JJJ%           jjj                   (001-366) day of year
          %TIME_HH%         hh                  (00-23)
          %TIME_MM%        mm               (00-59)
          %TIME_SS%            ss                  (00-59)
MAKEFILE: Fix Linux build when pcap.h isn't available but SDL is.  Fix for Issue #97
SCP: Fix for %DATE_WW% and %DATE_WYYYY% computation on the first days of a year after a leap year.