all: use "reports whether" consistently instead of "returns whether"

Follow-up for CL 147037 and after Brad noticed the "returns whether"
pattern during the review of CL 150621.

Go documentation style for boolean funcs is to say:

    // Foo reports whether ...
    func Foo() bool

(rather than "returns whether")

Created with:

    $ perl -i -npe 's/returns whether/reports whether/' $(git grep -l "returns whether" | grep -v vendor)

Change-Id: I15fe9ff99180ad97750cd05a10eceafdb12dc0b4
Reviewed-on: https://go-review.googlesource.com/c/150918
Run-TryBot: Tobias Klauser <[email protected]>
Reviewed-by: Brad Fitzpatrick <[email protected]>

Author: tklauser

dwarf/line.go

@@ -590,7 +590,7 @@ func (r *LineReader) SeekPC(pc uint64, entry *LineEntry) error {
 	}
 }
 
-// pathIsAbs returns whether path is an absolute path (or "full path
+// pathIsAbs reports whether path is an absolute path (or "full path
 // name" in DWARF parlance). This is in "whatever form makes sense for
 // the host system", so this accepts both UNIX-style and DOS-style
 // absolute paths. We avoid the filepath package because we want this