File and directory primitives are severely broken

[Ian Piumarta]

Many of the file primitives allocate 1000-byte buffers for path names  
and pass their address to functions defined in support code, without  
passing their length or in any way trying to agree with support code  
about what the maximum length of a path name should be.  Directory  
primitives are worse: in one place a 256-byte buffer is allocated on  
the stack and expected to be sufficient for any directory entry.

Here's the portable way to fix this without changing any of the APIs.

I suggest everyone who maintains a platform check that they do indeed  
have <limits.h> (its availability is mandated by ANSI C) and once  
nobody reports it missing that this header file be included at the  
beginning of sq.h.  All occurrences of

	char buf[1000];
or
	char entryName[256];

that allocate space for path names in the file and directory prims  
should then be changed to read

	char buf[PATH_MAX];

before one of these ticking time bombs explodes in someone's face.

FWIW: The Unix VM uses PATH_MAX religiously when checking for over- 
length, or allocating space for, path names.  (This is the correct  
thing to do.)  On OS X PATH_MAX is 1024; on Linux it's 4096.

Cheers,
Ian