A bunch less warnings by deleting unused variables or marking
variables or functions as unused.

geometry.c:525: warning: 'determinate' defined but not used
prop_sdarray.c: In function 'darray_prop_edit':
prop_sdarray.c:247: warning: unused variable 'prop'
diacellrendererproperty.c:203: warning: unused variable 'cellproperty'
class.c: In function 'umlclass_allow_resizing_callback':
class.c:384: warning: statement with no effect
class.c:385: warning: statement with no effect
class.c: In function 'umlclass_draw_operationbox':
class.c:972: warning: unused variable 'wrapping_needed'
class.c: In function 'umlclass_calculate_data':
class.c:1685: warning: unused variable 'min_box_width'
diacairo-renderer.c: In function '_ellipse':
diacairo-renderer.c:579: warning: unused variable 'co'
  (also removing a bbunch of obsolete code)
diacairo-print.c:35: warning: 'count_objs' defined but not used
diapsft2renderer.c: In function 'draw_string':
diapsft2renderer.c:345: warning: unused variable 'width'
pydia-property.c: In function 'PyDia_set_Arrow':
pydia-property.c:264: warning: unused variable 'i'
render_libart.c: In function 'new_libart_renderer':
render_libart.c:86: warning: unused variable 'renderer_type'
dia-render-script-import.c:38: warning: '_parse_real' defined but not
used
dia-render-script-import.c:49: warning: '_parse_point' defined but not
used
dia-render-script-import.c:65: warning: '_parse_points' defined but not
used
dia-render-script-import.c:90: warning: '_parse_bezpoints' defined but
not used
dia-render-script-import.c:121: warning: '_parse_color' defined but not
used
commands.c: In function 'dialogs_properties_callback':
commands.c:1131: warning: unused variable 'selected'
diagram_tree_view.c: In function '_dtv_locate_item':
diagram_tree_view.c:363: warning: unused variable 'layer'
dia-application.c: In function 'dia_application_class_init':
dia-application.c:61: warning: unused variable 'object_class'
test-boundingbox.c: In function 'main':
test-boundingbox.c:131: warning: unused variable 'plugins'