oniguruma: Out-of-bounds heap write in bitset_set_range()

An issue was discovered in Oniguruma 6.2.0, as used in Oniguruma-mod in Ruby through 2.4.1 and mbstring in PHP through 7.1.5. A heap out-of-bounds write occurs in bitsetsetrange during regular expression compilation due to an uninitialized variable from an incorrect state transition. An incorrect...