Cleanup lldb amd64 support.

Cleanup lldb amd64 support.

- Remove watchpoint support since we do not support hardware watchpoints.

- Support floating point regsisters in the ReadAll/WriteAll interface.

- Standardize the sizes used in GerGPRSize() and GetFPRSize() to correspond
  to the sizes we get from ptrace.

- Fix the r/w of the mmx registers to map onto the st fp registers instead
  of xmm registers.

- Normalize some variable names to be architecture neutral.

ok patrick@