Change struct breakpoint to m64p_breakpoint.

The breakpoint struct name was inconsistent with the rest of the `m64p' prefixed
declarations.

The API DebugBreakpointCommand was also changed to specify a m64p_breakpoint
pointer instead of a void pointer. There are no uses for the pointer other than
for referencing a breakpoint.
Wrap breakpoint flags into m64p_dbg_bkp_flags enum.

The unused conditional and counter flags have been removed to avoid any
confusion until those features are added.

An `M64P' prefix is also added to the flags. This matches the style of other
API flags.
Merge pull request #29 from wnayes/bpt-api-type

Change struct breakpoint to m64p_breakpoint.
Merge pull request #30 from wnayes/bpt-flag-enum

Wrap breakpoint flags into m64p_dbg_bkp_flags enum.
Fixed ARM build error
Using __buitin_bswap32() for sl() produces faster code on ARM with GCC 4.7