Method bit_ops

Perform GET, CLR, SET, and ADD operations on the Handle_Sets. GET = 1, Retrieve current value SET = 2, Set value of bits to new mask (changes the entire mask) ADD = 3, Bitwise "or" the value into the mask (only changes enabled bits) CLR = 4 Bitwise "and" the negation of the value out of the mask (only changes enabled bits) Returns the original mask. Must be called with locks held.