Update Gerard Holzmann's Spin from version 4.3.0 (22 June 2007)
to 6.1.0 (4 May 2011).

The manual was carefully updated to reflect formatting differences.

For information, here are the differences between the original version
from Gerard Holzmann and this Plan 9 version of Spin.

diff /sys/src/cmd/spin.orig/main.c /sys/src/cmd/spin/main.c
103c103
< 				#define CPP	"/lib/cpp"	/* classic Unix systems */
---
> 				#define CPP	"/bin/cpp"	/* classic Unix systems */
540c540
< {	extern int yychar; extern char yytext[];
---
> {	extern char yytext[];
548,552d547
< 	if (yychar > 0)
< 	{	printf("	saw '");
< 		explain(yychar);
< 		printf("'");
< 	}
diff /sys/src/cmd/spin.orig/pangen1.c /sys/src/cmd/spin/pangen1.c
19,23d18
< #ifdef SOLARIS
< #include <sys/int_limits.h>
< #else
< #include <stdint.h>
< #endif
157c152
< 		if (i <= UINT8_MAX)	/* in stdint.h = UCHAR_MAX from limits.h */
---
> 		if (i <= 255)	/* in stdint.h = UCHAR_MAX from limits.h */
159c154
< 		} else if (i <= UINT16_MAX)	/* really USHRT_MAX from limits.h */
---
> 		} else if (i <= 65535)	/* really USHRT_MAX from limits.h */
diff /sys/src/cmd/spin.orig/spin.h /sys/src/cmd/spin/spin.h
18,20d17
< #ifndef PC
< #include <memory.h>
< #endif