Don't double-encode URLs before parsing them

<https://code.google.com/p/macvim/issues/detail?id=316> wasn't a bug.

When you're constructing a URL, you *should* end up escaping URL-unsafe
characters twice: once for the `file:` URL and once for the `mvim:` URL.
Escaping it inside MacVim breaks legit URLs with escapes at the `mvim:` level.
updated for version 7.4.008
Problem:    New regexp engine can't be interrupted.
Solution:   Check for CTRL-C pressed. (Yasuhiro Matsumoto)
Added tag v7-4-008 for changeset b04bdb2c5fce
updated for version 7.4.009
Problem:    When a file was not decrypted (yet), writing it may destroy the
	    contents.
Solution:   Mark the file as readonly until decryption was done. (Christian
	    Brabandt)
Added tag v7-4-009 for changeset 8b5d80861c5e
updated for version 7.4.010
Problem:    Crash with invalid argument to mkdir().
Solution:   Check for empty string. (lcd47)
Added tag v7-4-010 for changeset bb358cc41d92
updated for version 7.4.011
Problem:    Cannot find out if "acl" and "xpm" features are supported.
Solution:   Add "acl" and "xpm" to the list of features. (Ken Takata)
Added tag v7-4-011 for changeset 54e66395831c
updated for version 7.4.012
Problem:    MS-Windows: resolving shortcut does not work properly with
	    multi-byte characters.
Solution:   Use wide system functions. (Ken Takata)
Added tag v7-4-012 for changeset 8e28c23e482c
updated for version 7.4.013
Problem:    File name buffer too small for utf-8.
Solution:   Use character count instead of byte count. (Ken Takata)
Added tag v7-4-013 for changeset 07737d3aa817
updated for version 7.4.014
Problem:    MS-Windows: check for writing to device does not work.
Solution:   Fix #ifdefs. (Ken Takata)
Added tag v7-4-014 for changeset 9801d06e7b4c
updated for version 7.4.015
Problem:    MS-Windows: Detecting node type does not work for multi-byte
	    characters.
Solution:   Use wide character function when needed. (Ken Takata)
Added tag v7-4-015 for changeset a7478f9f2551
updated for version 7.4.016
Problem:    MS-Windows: File name completion doesn't work properly with
	    Chinese characters. (Yue Wu)
Solution:   Add fname_casew(). (Ken Takata)
Added tag v7-4-016 for changeset 8d5cd0ec3e71
Merge branch 'vim'