all: be more idiomatic when documenting boolean return values.

Phrases like "returns whether or not the image is opaque" could be
describing what the function does (it always returns, regardless of
the opacity) or what it returns (a boolean indicating the opacity).
Even when the "or not" is missing, the phrasing is bizarre.

Go with "reports whether", which is still clunky but at least makes
it clear we're talking about the return value.

These were edited by hand. A few were cleaned up in other ways.

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/11699043

src/pkg/regexp/regexp.go

@@ -375,21 +375,18 @@ func (re *Regexp) LiteralPrefix() (prefix string, complete bool) {
 	return re.prefix, re.prefixComplete
 }
 
-// MatchReader returns whether the Regexp matches the text read by the
-// RuneReader.  The return value is a boolean: true for match, false for no
-// match.
+// MatchReader reports whether the Regexp matches the text read by the
+// RuneReader.
 func (re *Regexp) MatchReader(r io.RuneReader) bool {
 	return re.doExecute(r, nil, "", 0, 0) != nil
 }
 
-// MatchString returns whether the Regexp matches the string s.
-// The return value is a boolean: true for match, false for no match.
+// MatchString reports whether the Regexp matches the string s.
 func (re *Regexp) MatchString(s string) bool {
 	return re.doExecute(nil, nil, s, 0, 0) != nil
 }
 
-// Match returns whether the Regexp matches the byte slice b.
-// The return value is a boolean: true for match, false for no match.
+// Match reports whether the Regexp matches the byte slice b.
 func (re *Regexp) Match(b []byte) bool {
 	return re.doExecute(nil, b, "", 0, 0) != nil
 }