Remove some unused macros from the rust codebase

Remove some unused macros from the rust codebase

Removes unused macros from:
  * libcore
  * libcollections
    The last use of these two macros was removed in commit
    b64c9d56700e2c41207166fe8709711ff02488ff
    when the char_range_at_reverse function was been removed.
  * librustc_errors
    Their last use was removed by commits
    2f2c3e178325dc1837badcd7573c2c0905fab979
    and 11dc974a38fd533aa692cea213305056cd3a6902.
  * libsyntax_ext
  * librustc_trans
    Also, put the otry macro in back/msvc/mod.rs under the
    same cfg argument as the places that use it.