does not compile on Mac OS X Snow Leopard

[Michal Szymanski]

ical-3.0.2 fails to compile on Mac OS X 10.6.8 (Snow Leopard) with GCC 4.2.1, Tcl/Tk 8.5.
'configure' succeeds but 'make' fails on

g++ -DHAVE_CONFIG_H -I. -I./types -I./time -g -O2 -MT libcalendar_a-item.o -MD -MP -MF .deps/libcalendar_a-item.Tpo -c -o libcalendar_a-item.o `test -f 'calendar/item.C' || echo './'`calendar/item.C
calendar/item.C: In member function ‘void Appointment::convert_tz(Date&, int&, bool_type) const’:
calendar/item.C:392: error: ‘strdupa’ was not declared in this scope
calendar/item.C:394: error: aggregate ‘tm t’ has incomplete type and cannot be defined
calendar/item.C:408: error: ‘tzset’ was not declared in this scope
calendar/item.C:411: error: ‘mktime’ was not declared in this scope
calendar/item.C:418: error: ‘tzset’ was not declared in this scope
calendar/item.C:420: error: ‘localtime’ was not declared in this scope
calendar/item.C:426: error: invalid use of incomplete type ‘struct tm’
calendar/item.C:394: error: forward declaration of ‘struct tm’
calendar/item.C:426: error: invalid use of incomplete type ‘struct tm’
calendar/item.C:394: error: forward declaration of ‘struct tm’
calendar/item.C:426: error: invalid use of incomplete type ‘struct tm’
calendar/item.C:394: error: forward declaration of ‘struct tm’
calendar/item.C:427: error: invalid use of incomplete type ‘struct tm’
calendar/item.C:394: error: forward declaration of ‘struct tm’
calendar/item.C:427: error: invalid use of incomplete type ‘struct tm’
calendar/item.C:394: error: forward declaration of ‘struct tm’
make[1]: *** [libcalendar_a-item.o] Error 1
make: *** [all] Error 2