Give fontio its own enable

.. the default is intended to be the equivalent of the original,
implementing `DISPLAYIO && TERMINALIO`.

This is a possible alternative to #6889, if I understand the intent.

py/circuitpy_defns.mk

@@ -323,6 +323,9 @@ endif
 ifeq ($(CIRCUITPY_TERMINALIO),1)
 SRC_PATTERNS += terminalio/% fontio/%
 endif
+ifeq ($(CIRCUITPY_FONTIO),1)
+SRC_PATTERNS += fontio/%
+endif
 ifeq ($(CIRCUITPY_TIME),1)
 SRC_PATTERNS += time/%
 endif

py/circuitpy_mpconfig.mk

@@ -390,6 +390,11 @@ CFLAGS += -DCIRCUITPY_SYNTHIO=$(CIRCUITPY_SYNTHIO)
 CIRCUITPY_TERMINALIO ?= $(CIRCUITPY_DISPLAYIO)
 CFLAGS += -DCIRCUITPY_TERMINALIO=$(CIRCUITPY_TERMINALIO)
 
+ifeq ($(CIRCUITPY_DISPLAYIO),1)
+CIRCUITPY_FONTIO ?= $(CIRCUITPY_TERMINALIO)
+endif
+CFLAGS += -DCIRCUITPY_FONTIO=$(CIRCUITPY_FONTIO)
+
 CIRCUITPY_TIME ?= 1
 CFLAGS += -DCIRCUITPY_TIME=$(CIRCUITPY_TIME)
 

shared-bindings/fontio/__init__.c

@@ -57,4 +57,4 @@ const mp_obj_module_t fontio_module = {
     .globals = (mp_obj_dict_t *)&fontio_module_globals,
 };
 
-MP_REGISTER_MODULE(MP_QSTR_fontio, fontio_module, CIRCUITPY_DISPLAYIO && CIRCUITPY_TERMINALIO);
+MP_REGISTER_MODULE(MP_QSTR_fontio, fontio_module, CIRCUITPY_FONTIO);