Renamed INITBSS to INIT and INIT to ONCE.

The way we want to use the INITBSS segment - and especially the fact that it won't have the type bss on all ROM based targets - means that the name INITBSS is misleading. After all INIT is the best name from my perspective as it serves several purposes and therefore needs a rather generic name.

Unfortunately this means that the current INIT segment needs to be renamed too. Looking for a short (ideally 4 letter) name I came up with ONCE as it contains all code (and data) accessed only once during initialization.

libsrc/nes/cputc.s

@@ -75,10 +75,10 @@ putchar:
         jmp     ppubuf_put
 
 ;-----------------------------------------------------------------------------
-; Initialize the conio subsystem. Code goes into the INIT segment, which may
+; Initialize the conio subsystem. Code goes into the ONCE segment, which may
 ; be reused after startup.
 
-.segment        "INIT"
+.segment        "ONCE"
 
 initconio:
         jsr     ppuinit

libsrc/nes/irq.s

@@ -6,7 +6,7 @@
 
 ; ------------------------------------------------------------------------
 
-.segment        "INIT"
+.segment        "ONCE"
 
 initirq:
         rts

libsrc/nes/mainargs.s

@@ -10,10 +10,10 @@
 
 
 ;---------------------------------------------------------------------------
-; Get possible command-line arguments. Goes into the special INIT segment,
+; Get possible command-line arguments. Goes into the special ONCE segment,
 ; which may be reused after the startup code is run
 
-.segment        "INIT"
+.segment        "ONCE"
 
 .proc   initmainargs