add (mouse) enter and leave signals

* xpdf/gpdf-link-canvas-item.cc
(gpdf_link_canvas_item_mouse_enter)
(gpdf_link_canvas_item_mouse_leave)
(gpdf_link_canvas_item_class_init): add (mouse) enter and leave
signals

* xpdf/gpdf-link-canvas-item.h: add signal slots for enter and
leave

* xpdf/tests/test-links.cc (link_item_enter_leave): test for the
signals

* xpdf/Makefile.am: now the marshallers sources are not shipped
with the dist and correctly build when needed, finally

* configure.in: version 0.102.99