New script to catch unresolved merge conflicts

Added a script which examines files for strings which should not be
in source.  This was prompted by the delivery of code in which
merge conflicts had not been resolved.

File sql/regress/catman1/TEST138 had

  =======
  <<<<<<< HEAD
  grant component privilege "CREATE" on SQL_OPERATIONS to "PUBLIC";
  get privileges on component sql_operations for "PUBLIC";
  =======
  >>>>>>> bff2742... ANSI Schema

Help text is:

  Usage: find-bad-source.sh [-q] [<commit-id> ]

   <commit-id>    If omitted, use HEAD.

   -q             Quiet mode.  Do not report all examined files
                and the context for the found lines.

  Search source files for bad strings using this command:

        egrep -rnH -e'<<<<<<<.*HEAD|>>>>>>>>.*HEAD'

  This should be run at the top level of a git repo.

Change-Id: Iab9cb58177d0e9c7f20be60fb156d1f674df3786