Creates a new source link. The link source buffer is hbufSource. The link source line number is lnSource. The link target file is given as a path string in target_file. The link target line number is lnTarget.
Returns True if successful, or False if not. Target_file does not have to exist. The operation will not fail just because target_file does not exist. Also, target_file does not need to be open.
For consistent results, target_file should contain a fully qualified path name for a file. However, you may pass a simple file spec to this function and it will expand target_file based on what files are included in the current project and on the project symbol path.
Source Links are destroyed when the source buffer closes, or when the source line is deleted.