New patch 0009 fixes O(L) line scanning in accessibilityLineForIndex:
and accessibilityRangeForLine: by adding a precomputed lineStartOffsets
array built once per cache rebuild. Queries go from O(L) linear scan
to O(log L) binary search.
README.txt: updated patch listing, text cache section, known limitations
(O(L) issue now resolved), stress test threshold raised to 50,000 lines.
