RFR: 8023476: Metaspace capacity > reserved

[Erik Helin]

Hi all,

this change is a first step to clean up the usage of words and bytes in
metaspace.cpp/hpp. The change includes:
- Appending function names with the unit of the size they return. All
  functions in MetaspaceAux returning bytes are now ending in _bytes and
  functions returning words ends in _words.
- Appending function that iterates over the ClassLoaderDataGraph with
  _slow. These functions have also been made private since they should
  only be used internally for verification purposes.
- Removing the function Metaspace::waste_bytes which isn't used
- Making sure MetaspaceAux::reserved_bytes actually returns bytes
  instead of words.

Webrev:
http://cr.openjdk.java.net/~ehelin/8023476/webrev.00/

Testing:
- JPRT
- hotspot/test/gc/metaspace

Thanks,
Erik