[Cook] [BUG] symbolic links

[Lev S Bishop]

cook seems to have a few problems with symbolic links that cause cycles in 
the directory structure graph. Here's one example:

$ touch howto.cook
$ mkdir d
$ cd d
$ ln -s ../ q
$ cook -b ../howto.cook -fpu
$ cook -b ../howto.cook -fpu

It segfaults. Here's a stack trace:
#0  symtab_query (stp=0x0, key=0xa054d70) at common/symtab.c:193
#1  0x00409467 in fp_find_update (sdp=0xa0542a0, file=0xa054d70, fp=0x22e3b0) at cook/fingerprint/find.c:298
#2  0x0040998c in fingerprint_gram_parse () at cook/fingerprint/gram.y:134
#3  0x0040969e in fp_gram (sdp=0xa0542a0, filename=0xa054270) at cook/fingerprint/gram.y:100
#4  0x0040a529 in fp_subdir_read (this=0xa0542a0) at cook/fingerprint/subdir.c:153
#5  0x0040929c in fp_find_subdir (dirname=0xa0534d0, ok_to_read=1) at cook/fingerprint/find.c:115
#6  0x00409010 in fp_tweak () at cook/fingerprint.c:144
#7  0x004162ea in main (argc=4, argv=0xa052ab0) at cook/main.c:725