Remove unused ftx font backend driver
* src/ftxfont.c: Remove file. * admin/notes/font-backend: * configure.ac: * src/Makefile.in: * src/deps.mk (ftxfont.o): * src/font.c (syms_of_font): * src/font.h (top-level, font_property_index): * src/xfns.c (Fx_create_frame, x_create_tip_frame): Remove unused ftx font backend driver. Thanks to Glenn Morris for pointing out that it can be removed. (Bug#34663)