port/sysfile.c		1990/0227		Created.
		1990/0321
		1990/03292
		1990/0513
		1990/0617
		1990/0703
		1990/08141
		1990/0821
		1990/0822
		1990/0918
		1990/1004
		1990/1009
		1990/11211
		1990/1126
		1990/1210		Created.
		1991/0221		Bug fix: check for invalid file descriptors.
		1991/0319		Disallow seek on pipe.
		1991/0411		Bug fix: add explicit read lock and write lock instead of using channel's qlock.
		1991/0417		Debugging: acquire both locks during read and write.
		1991/0419		Remove debugging.
		1991/0501		Whitespace edit.
		1991/0614		Possible semantics change: insert poperrors in read, write, remove, despite comment at top of file.
		1991/0615		Semantics change: require names to be at most NAMELEN in length, instead of unlimited.
		1991/0705
		1991/0706
		1991/0904
		1991/1011
		1991/1018
		1991/1101
		1991/1107
		1992/0111		Move error.h to ../port. Change errors to actual strings.
		1992/0114
		1992/0312
		1992/0321		Move lib.h to ../port.
		1992/0520
		1992/0607
		1992/0619
		1992/0711
		1992/0720
		1992/0817
		1992/0825
		1993/0209
		1993/0317
		1993/0318
		1993/0330
		1993/0501
		1993/1004
		1993/1014
		1993/1111
		1994/0321
		1994/0402
		1994/0405
		1994/0406
		1994/0611
		1994/0616
		1994/0622
		1997/0327
		1997/0408
		1997/0529
		1997/0603
		1997/0606
		1997/1104
		1997/1105
		1997/1203
		1997/1205
		1997/1208
		1998/0221
		1998/0224
		1998/0319		Add vlong seek system call.
		1998/0320		Bug fix: use low bits of length instead of high.
		1998/0326		Change VSEEK system call to return vlong.
		1998/0403		Bug fix: incref channel during sseek.
		1998/0512		Whitespace edit.
		1998/0829
		1998/0901
		1998/0915
		1998/0922
		1998/0923
		1999/0122
		1999/0528
		1999/0629
		1999/0709
		1999/0717
		1999/0718
		1999/0811
		1999/0812
		1999/1105
		2000/0209
		2000/0215
		2000/0322
		2000/0505
		2000/0719
		2000/0814
		2001/0207
		2001/0223
		2001/0502
		2001/0527
		2001/0528
		2001/0727
		2001/0728
		2001/0731
		2001/0819
		2001/0820
		2001/0822
		2001/0912
		2001/0919
		2001/1111
		2001/1118
		2001/1212
		2001/1230
		2002/0104		Add extra parameter to walk.
		2003/0326
		2003/0509
		2003/0510