Update .gitignore
Update NEWS
Update bash_completion
Bump up version number to 1.18.4
Fix mingw32 build with gcc 4.8.2

Now mingw-w64 C++ compiler defines __USE_MINGW_ANSI_STDIO to 1, we
have to follow it as well.  We hope that mingw version of stdio
function behaves like Linux ones.  We have not tested them thoroughly
yet.  pthread for windows defines its own HAVE_STRUCT_TIMESPEC macro.
To avoid warning, we rename our version of it as
HAVE_A2_STRUCT_TIMESPEC.
Update pre-built README