-Yshow-member-pos, print the positions of members.

Here for instance is a command line which leverages the
output of this option to print the method bodies of all
methods called 'transformInfo' found under src. Given
1500 source files it accomplishes this in four seconds,
thanks to -Ystop-after:parser.

```
% scalac -Yshow-member-pos sed -Ystop-after:parser \
    $(find src/compiler -name '*.scala') | \
    grep transformInfo | sed 's/ # .*//;' | \
    while read line; do echo "// $line" && gsed -n $line && echo; done
```
Or more simply, the start/end lines of each member of Random:
```
% scalac -Yshow-member-pos "" ./src/library/scala/util/Random.scala
./src/library/scala/util/Random.scala
20,134               class Random
 33                  def nextBoolean
 38                  def nextBytes
 43                  def nextDouble
 48                  def nextFloat
 54                  def nextGaussian
 59                  def nextInt
 65                  def nextInt
 70                  def nextLong
 81,89               def nextString
  82,86              def safeChar
   83                val surrogateStart
   84                val res
 94,98               def nextPrintableChar
 [snip]
```
It makes me sad I'm always in the position of having to hack
the compiler to do this sort of thing. All we need is something
like -Yinsert-phase:Foo where Foo is a class implementing a
(Phase, Tree) => Tree method, and the compiler runs all the
unit.bodies through it after each phase, and then one could
easily accomplish this in the privacy of one's own compiler.