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 7.4.001
Problem:    Character classes such as [a-z] to not react to 'ignorecase'.
	    Breaks man page highlighting. (Mario Grgic)
Solution:   Add separate items for classes that react to 'ignorecase'.  Clean
	    up logic handling character classes.  Add more tests.
Added tag v7-4-001 for changeset 3e9107b86b68
updated for version 7.4.002
Problem:    Pattern with two alternative look-behind matches does not match.
	    (Amadeus Demarzi)
Solution:   When comparing PIMs also compare their state ID to see if they are
	    different.
Added tag v7-4-002 for changeset e29f11399cce
updated for version 7.4.003
Problem:    Memory access error in Ruby syntax highlighting. (Christopher Chow)
Solution:   Refresh stale pointer. (James McCoy)
Added tag v7-4-003 for changeset 560a6a232950
updated for version 7.4.004
Problem:    When closing a window fails ":bwipe" may hang.
Solution:   Let win_close() return FAIL and break out of the loop.
Added tag v7-4-004 for changeset f6247eaf4e1d
updated for version 7.4.005
Problem:    Using "vaB" while 'virtualedit' is set selects the wrong area.
	    (Dimitar Dimitrov)
Solution:   Reset coladd when finding a match.
Added tag v7-4-005 for changeset 3640cf4c0d4b
updated for version 7.4.006
Problem:    mkdir("foo/bar/", "p") gives an error message. (David Barnett)
Solution:   Remove the trailing slash. (lcd)
Added tag v7-4-006 for changeset 2374a05efe20
updated for version 7.4.007
Problem:    Creating a preview window on startup leaves the screen layout in a
	    messed up state. (Marius Gedminas)
Solution:   Don't change firstwin. (Christian Brabandt)
Added tag v7-4-007 for changeset 4fe1dfc7014e
Merge branch 'vim'
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