[ms] [llvm-ml] Support for `NEAR` in `EXTERN` directives

[MisterDA]

$ cat > test.asm <<EOF
      EXTERN  my_symbol_near:NEAR
      EXTERN  my_symbol_far:FAR
      
      .CODE
      call my_symbol_near
      END
EOF
$ build/bin/llvm-ml64 -c -Fo test.obj test.asm
test.asm:1:32: error: unrecognized type in directive 'extern'
        EXTERN  my_symbol_near:NEAR
                              ^
test.asm:2:31: error: unrecognized type in directive 'extern'
        EXTERN  my_symbol_far:FAR
                             ^

EXTERN is defined as:

extern name:type {,name:type...}

The type for symbols is documented by Microsoft to be ABS or PROC, but I've found other documents noting:

Type may be any of near, far, proc, byte, word, dword, qword, tbyte, abs (absolute, which is a constant), or some other user defined type.

I'm interested in support for near.
Cf #131707 cc @ericastor

[ericastor]

I'll fix this in a followup PR to #131707; I want to land basic PROC NEAR/FAR support first.