Facilitate cross compilation, and simplify own makefile

Various changes to permit Squish to run under the (Matrix) Brandy interpreter when a build is performed on a cross-compilation host. Also simplify Squish's own makefile (requires RiscOS/BuildSys!32 (merged)).

bas/Squish

  ALIGN
  EQUD 0
 
-.adr  EQUD 0  ; address of found identifier, or where to store link to new identifier
-.fadr EQUD -1 ; 1 = identifier found, 0 = identifier not found
+.adr  EQUD 0  ; = 1 if found identifier, else = where to store link to new identifier
+.fadr EQUD -1 ; = address of found identifier, else = unchanged from entry
 ]
 NEXT A
 
 PROClog_str(i$)
 ENDPROC
 
-DEF PROCtok(A%)
-CALLgettoken
-N%=!tst
-ENDWHILE
-ENDPROC
-
-DEF PROCextok(A%,?nxt)
-CALLgettoken
-N%=!tst
-i$=""
-WHILE ?N%<127 AND ?N%>31
-  i$+=CHR$ ?N%
-  N%+=1
-ENDWHILE
-PROClog_str(i$)
-ENDPROC
-
 DEF PROCwrite_program
 qa%=5
 linebase%=0

[Ben Avison]

It turned out that if you did an installation starting from version 1, it didn't work correctly when cross-compiling. This was because the special Brandy variables ARGC and ARGV$() were getting renamed (and in fact, the keep file wasn't being specified, so so were lots of single-character integer variables, which probably hurt performance).

I've also now enabled GitLab CI/CD.