[Gm2] column information in errors and new switch -fxcode

[Gaius Mulley]

Hi,

here are the latest set of changes from the ChangeLog:

        * gm2/NEWS:  updated.
        * gm2/gm2.texi:  documented new -fxcode option and minor
          fixes.
        * gm2/lang-options.h:  added -fxcode to list of options.
        * gm2/lang.opt:  added -fxcode to list of options.
        * gm2/m2.flex:  added m2flex_GetColumnNo.
        * gm2/gm2-compiler/M2Error.mod:  OutString modified to
          use column and produce GNU and Xcode format errors.
        * gm2/gm2-compiler/M2LexBuf.def:  export column
          related procedures.
        * gm2/gm2-compiler/M2LexBuf.mod:  introduced recording
          of the column position.  GetColumnNo, TokenToColumnNo
          new procedures.
        * gm2/gm2-compiler/M2Options.def:  added Xcode.
        * gm2/gm2-compiler/M2Options.mod:  set Xcode accordingly.
        * gm2/gm2/gm2-compiler/M2Students.mod:  fixed spelling
          mistake.
        * gm2/gm2-compiler/P1SymBuild.mod:  tidied up error
          message.
        * gm2/gm2-compiler/SymbolTable.mod:  ditto.
        * gm2/gm2-compiler/m2flex.def:  added GetColumnNo
          procedure.

Column information is now given when an error or warning is issued.
I've added a new option -fxcode which generates errors and warnings
in a xcode compatible format.

regards,
Gaius