Forward reference needs override

An expression containing a forward-referenced variable resulted in more
code being required than Turbo Assembler anticipated. This can happen
either when the variable is unexpectedly a far address for a JMP or CALL
or when the variable requires a segment override in order to access it.
For example,

     ASSUME cs:DATA 
     call A            ;presume near call 
   PROC A FAR          ;oops, it's far

     mov ax,[memvar]   ;doesn't know it needs override
   SEGMENT DATA
   memvar DW  ?        ;oops, needs override

Correct this by explicitly supplying the segment override or FAR override.