added memtop to machine definition and asm source code check

added %memtop directive

codeGenCpu6502/src/prog8/codegen/cpu6502/ProgramAndVarsGen.kt

@@ -284,6 +284,8 @@ internal class ProgramAndVarsGen(
                 asmgen.out("  .cerror * > ${relocatedBssEnd.toHex()}, \"too many data for slabs_BSS section\"")
             }
         }
+        asmgen.out("  ; memtop check")
+        asmgen.out("  .cerror * > ${options.memtopAddress.toHex()}, \"Program too long by \", * - ${options.memtopAddress.toHex()}, \" bytes, memtop=${options.memtopAddress.toHex()}\"")
     }
 
     private fun block2asm(block: PtBlock) {

codeGenCpu6502/test/TestCodegen.kt

@@ -26,7 +26,8 @@ class TestCodegen: FunSpec({
             floats = true,
             noSysInit = false,
             compTarget = target,
-            loadAddress = target.machine.PROGRAM_LOAD_ADDRESS
+            loadAddress = target.machine.PROGRAM_LOAD_ADDRESS,
+            memtopAddress = 0xffffu
         )
     }