Change strwhere to work conventionally

Individual characters are passed to predicate (as single-character strings), rather than substrings from current index to end.

Before:

strwhere("abcd", { print($0); true })
"abcd"
"bcd"
"cd"
"d"
[0, 1, 2, 3]

after:

strwhere("abcd", { print($0); true })
"a"
"b"
"c"
"d"
[0, 1, 2, 3]

Scripts modified to track.