Implement bit field clear/insert. Constant pool fixes

Change-Id: Ie14c0679db2d8fa3a9a6a24d5217c5d9c4e7fd35
Fix vstmia instruction selection/emission problem.

Change-Id: I34137e9a3490fe8859201f727cce6df81ad93173
Add "*2" to vstmia

Change-Id: I95e6eda70555757ca9378d508d0470b5ef0f64b2
3 fixes:
 1. ubfx (lsb, width and src)
 2. vbfx
 3. vstm (If Si, NumRegs shouldn't be doubled. If Di, NumRegs *= 2)

Change-Id: Ib5d8f5498f069f597c7af8d2cf1a293d15ddf484
Fix build