Define snprintf as _snprintf when under the influence of _MSC_VER.
Define int32_t and friends as __int32 and friends when under the influence of _MSC_VER.
Make include of unistd.h conditional on HAVE_UNISTD_H.
Don't AC_SUBST a dozen different FOO_CFLAGS and FOO_LIBS. Instead, incrementally build up just CAIRO_CFLAGS and CAIRO_LIBS.
Don't list flags that should get picked up via dependency information through Requires.
Add description of move_to_show_surface.