Renamed mailcore::logEnabled and mailcore::logInternal to MCLogEnabled
and MCLogInternal as discussed in MailCore/mailcore2#118.
* Followed the diff in MailCore/mailcore2#124.
* Renamed the implementation file from .cc to .c
* Added `extern "C" {}` around header declaration.
Updated mailcore::logEnabled to MCLogEnabled in logInternalv.
Updated remaining references to mailcore::logEnabled.
Including the stdbool header.
* As per http://stackoverflow.com/a/1921557/339925
Updated type of MCLogEnabled to int instead of bool.
Merge pull request #169 from paulyoung/mclog

make MCLog compatible with plain C.