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/geos-common/conio/_scrsize.s

@@ -14,7 +14,7 @@
                       
         .include "geossym.inc"
 
-.segment        "INIT"
+.segment        "ONCE"
 
 initscrsize:
 .ifdef __GEOS_CBM__

libsrc/geos-common/system/mainargs.s

@@ -18,7 +18,7 @@
             .include "const.inc"
             .include "geossym.inc"
 
-.segment        "INIT"
+.segment        "ONCE"
 
 ; Setup arguments for main