cmd/compile: convert dxxx to dxxxLSym

cmd/compile: convert dxxx to dxxxLSym

This is an automated refactoring to eliminate
all dxxx calls in gc/obj.go that accept types.Sym
instead of obj.LSym parameters.

The refactoring was of the form:

gorename -from '"cmd/compile/internal/gc".duintxx' -to Duintxx
gorename -from '"cmd/compile/internal/gc".duintxxLSym' -to DuintxxLSym
eg -t t.go -w cmd/compile/internal/gc
gofmt -r 'DuintxxLSym -> duintxxLSym' -w cmd/compile/internal/gc

where t.go looked like:

func before(s *types.Sym, off int, v uint64, wid int) int {
	return gc.Duintxx(s, off, v, wid)
}

func after(s *types.Sym, off int, v uint64, wid int) int {
	return gc.DuintxxLSym(s.Linksym(), off, v, wid)
}

The rename/gofmt shenanigans were to work around
limitations and bugs in eg and gorename.

The resulting code in reflect.go looks temporarily ugly,
but it makes refactoring and cleanup opportunities
much clearer.

Next step is to rename all the dxxx methods to rename the -LSym suffix
and clean up reflect.go.

The renaming is left for a separate CL to make the changes in
this CL more obvious, and thus hopefully easier to review.

Passes toolstash-check.

Change-Id: Ib31a2b6fd146ed03a855d20ecb0433f0f74e2f10
Reviewed-on: https://go-review.googlesource.com/41396
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>