updated to 7.4.307

updated to 7.4.307

7.4.296  can't run tests on Solaris
7.4.297  memory leak from result of get_isolated_shell_name()
7.4.298  can't have a funcref start with "t:"
7.4.299  when running configure twice DYNAMIC_PYTHON_DLL becomes empty
7.4.300  the way config.cache is removed doesn't always work
7.4.301  (after 7.4.280) scrolling problem when loading a session file
7.4.302  signs don't show up after filler lines
7.4.303  double-width chars on the command line sometimes truncated
7.4.304  cannot always use Python with Vim
7.4.305  making 'ttymouse' empty causes problems
7.4.306  getchar(0) does not return Esc
7.4.307  can't build without the +termresponse feature