Switch to assembler for cputc implementation.

libsrc/c1p/extzp.s

@@ -0,0 +1,23 @@
+;
+; Additional zero page locations for the Challenger 1P.
+; NOTE: The zeropage locations contained in this file get initialized
+; in the startup code, so if you change anything here, be sure to check
+; not only the linker config, but also the startup file.
+;
+
+; ------------------------------------------------------------------------
+
+        .include        "extzp.inc"
+
+.segment        "EXTZP" : zeropage
+
+; The following values get initialized from a table in the startup code.
+; While this sounds crazy, it has reasons that have to do with modules (and
+; we have the space anyway). So when changing anything, be sure to adjust the
+; initializer table
+CURS_X:         .byte   0
+CURS_Y:         .byte   0
+SCR_LINELEN:    .byte   24
+SCREEN_PTR:     .res    2
+
+; size 5