Since this is limited to ffs, use ufsinfo_t instead of ino_t.

Since this is limited to ffs, use ufsinfo_t instead of ino_t.
Grow the array of cached inodes exponentially instead of arithmetically.
Prefer sizeof(*pointer) over sizeof(type) in mallocs.
Don't leak memory in searchdir().
Fix multiple bugs in the handling of indirect blocks, including reuse of
a static buffer in a recursive function and failure to track the remaining
size of the directory blocks to process

Tested with a directory *doubly* indirect block!
ok krw@