Force re-align PC/R15 operations

[matanlurey]

E.g. BRANCH opCodes, or MOV/ALU/LDR with Rd=R15.

• For ARM: Low-bits of the target usually 0, force-align by clearing lower 2-bits.
• For THUMB: Low bit of the target may/should/must be set, the bit is (or is not) interpreted as thumb-bit
  (depending on the opCode), and R15 is then forcibly aligned by clearing the lower bit.

... in short, R15 will always be forcibly aligned, so mis-aligned branches won't have effect on subsequent opcodes that use R15 (or R15+disp) as an operand.