shell32: Better handle long URLs.
Currently ShellExecuteA() doesn't work for opening very long (>1024 chars) URLs. Commit fbf9cf6ebadc7d50c8fb7a130851c3658607b343 ("shell32: Make sure wcmd has enough space to hold the string.") started fixing it, but that is not enough.
This MR fixes two other issues on the way and lets ShellExecuteA() actually started winebrowser (with default registry) with the URL correctly relayed.