Can get stack overflow on machines with big longs.
 [rsc] --rw-rw-r-- M 140560 glenda sys 18335 Nov  1 07:36 sys/src/cmd/troff/tdef.h
	/n/sourcesdump/2005/1101/plan9/sys/src/cmd/troff/tdef.h:169,175 - 
	/n/sourcesdump/2005/1102/plan9/sys/src/cmd/troff/tdef.h:169,175
	  #define	NEV	3	/* environments */
	  #define	EVLSZ	10	/* size of ev stack */
	  
	- #define	STACKSIZE (6*1024)	/* stack for macros and strings in progress */
	+ #define	STACKSIZE (12*1024)	/* stack for macros and strings in progress */
	  #define	NHYP	10	/* max hyphens per word */
	  #define	NHEX	512	/* byte size of exception word list */
	  #define	NTAB	100	/* tab stops */