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/plus4/mainargs.s

@@ -32,10 +32,10 @@ MAXARGS  = 10                   ; Maximum number of arguments allowed
 REM      = $8f                  ; BASIC token-code
 NAME_LEN = 16                   ; Maximum length of command-name
 
-; 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"
 
 initmainargs:
 
@@ -125,7 +125,7 @@ done:   lda     #<argv
         stx     __argv + 1
         rts
 
-.segment        "INITBSS"
+.segment        "INIT"
 
 term:   .res    1
 name:   .res    NAME_LEN + 1