Changes implementations of proc.Registers interface and the
op.DwarfRegisters struct so that floating point registers can be loaded
only when they are needed.
Removes the floatingPoint parameter from proc.Thread.Registers.
This accomplishes three things:
1. it simplifies the proc.Thread.Registers interface
2. it makes it impossible to accidentally create a broken set of saved
registers or of op.DwarfRegisters by accidentally calling
Registers(false)
3. it improves general performance of Delve by avoiding to load
floating point registers as much as possible
Floating point registers are loaded under two circumstances:
1. When the Slice method is called with floatingPoint == true
2. When the Copy method is called
Benchmark before:
BenchmarkConditionalBreakpoints-4 1 4327350142 ns/op
Benchmark after:
BenchmarkConditionalBreakpoints-4 1 3852642917 ns/op
Updates #1549
Implement debugging function for 386 on linux with reference to AMD64.
There are a few remaining problems that need to be solved in another time.
1. The stacktrace of cgo are not exactly as expected.
2. Not implement `core` for now.
3. Not implement `call` for now. Can't not find `runtime·debugCallV1` or
similar function in $GOROOT/src/runtime/asm_386.s.
Update #20
