The program must be compiled with the GtkSpell C flags and built with the GtkSpell libs. Depending on how your program is compiled, you must include the module gtkspell-2.0 along with gtk+-2.0 in your calls to pkg-config.

In configure.ac, modify the call to PKG_CHECK_MODULES to include gtkspell-2.0, like this:

PKG_CHECK_MODULES(MYPROGRAM, gtk+-2.0 gtkspell-2.0)

FIXME: finish this.