M4, "[", and %destructor

[Joel E. Denny]

For this bison spec:

  %union { char * ptr; }
  %token <ptr> BRACKET "["
  %destructor { delete $$; } BRACKET
  %%
  start: BRACKET;
  %%

bison 2.0 fails with:

  NONE:0: /usr/local/bin/m4: ERROR: EOF in string
  bison: subsidiary program `/usr/local/bin/m4' failed (exit status 1)

bison 1.875 does not fail.

Joel