Support setting a breakpoint by FileSpec+Line+Column in the SBAPI.

This patch extends the SBAPI to allow for setting a breakpoint not
only at a specific line, but also at a specific (minimum) column. When
a column is specified, it will try to find an exact match or the
closest match on the same line that comes after the specified
location.

Differential Revision: https://reviews.llvm.org/D51461

llvm-svn: 341078