Summary: Add read and write functions for VSX, VMX and float registers and fix watchpoint size

Reviewers: clayborg

Reviewed By: clayborg

Subscribers: eugene, labath, clayborg, nemanjai, kbarton, JDevlieghere, anajuliapc, gut, lbianc, lldb-commits

Differential Revision: https://reviews.llvm.org/D39487
Patch by: Alexandre Yukio Yamashita <alexandre.yamashita@eldorado.org.br>

llvm-svn: 317329