fix handle leak in vp_pipe_open()

Also fix the possibility of double close problem. A handle returned by
_get_osfhandle() should not be passed to CloseHandle(), because it will
be closed automatically when closing the fd using _close().
Merge branch 'master' into topic/fix-handle-leak
fix get_command_name() issue

Additionally, use exepath() if available. (exepath() was added by 7.4.235.)
Merge pull request #129 from k-takata/topic/fix-get_command_name

fix get_command_name() issue
fix CRT handle leak

vp_pipe_open() should close hstdin, hstdout and hstderr.
Merge pull request #130 from k-takata/topic/fix-handle-leak

fix handle leak in vp_pipe_open()
improve documents

Use consistent name. (Mingw -> MinGW)
fix indent
fix indent in examples
update document about VC
break long lines

tw is set to 78.

Improve explanation of condition in vimproc#pgroup_open().
fix style

A space is inserted before a '('.
{is-pty} argument was missing
move a tag before a function name

This is the same style as the official Vim help.
improve documents
update internal command list

Add 'for' and 'if'.
Merge pull request #132 from k-takata/topic/update-internal-command-list

update internal command list
add a batch file for updating the DLL on Windows
Merge pull request #134 from k-takata/topic/improve-documents

improve documents
Merge pull request #133 from k-takata/topic/add-update-batch

add a batch file for updating the DLL on Windows