Rename log() to tor_log() for logging

This is meant to avoid conflict with the built-in log() function in
math.h.  It resolves ticket 7599.  First reported by dhill.

This was generated with the following perl script:

 #!/usr/bin/perl -w -i -p

 s/\blog\(LOG_(ERR|WARN|NOTICE|INFO|DEBUG)\s*,\s*/log_\L$1\(/g;

 s/\blog\(/tor_log\(/g;