Add libexecinfo for backtrace() on FreeBSD


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@202284 91177308-0d34-0410-b5e6-96231b3b80d8
Fix x86 32-bit register context definition to build properly on 32 and 64-bit hosts.

This fix changes thee x86 32-bit floating point register area to be
the proper size independent of the host platform.

Note as of this change list, this register context is not yet used
since selecting it exposes issues with watchpoint assertions.

Change by Matthew Gardiner.



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@202285 91177308-0d34-0410-b5e6-96231b3b80d8