Check for non-existent parameter expansions

[duncanamps]

Consider the following code

MyMac   MACRO   source, dest
        LD      HL,{ssource}
        LD      DE,{dest}
        CALL    CPYMEM
        ENDM
        :
        :
        MyMac OUTPUT, MESSAGE

Note the spelling mistake in LD HL,{ssource}. This is not picked up by the assembler and needs to be. It should check on macro substitutions for any { or } characters left over - this means they weren't expanded correctly.