curl unescape percent encoded characters before writing file

gistfile1.txt

Hi Daniel, I saw this comment thread and added the feature to decode the filename before writing similar to wget's behavior. Thus option -W seemed fitting and was available. 

so it can be used exactly like -O and -J:

`curl -W https://www.example.com/new%20pricing.htm`
> 'new pricing.htm'

curl -WJ http://test.greenbytes.de/tech/tc2231/attwithfnrawpctenca.asis
> foo-A.html

curl --remote-name-decode-all  https://www.example.com/new%20pricing.htm http://test.greenbytes.de/tech/tc2231/attwithfnrawpctenca.asis 
> 'new pricing.htm'
> attwithfnrawpctenca.asis 

curl --remote-name-decode-all  -J https://www.example.com/new%20pricing.htm http://test.greenbytes.de/tech/tc2231/attwithfnrawpctenca.asis 
> 'new pricing.htm'
> foo-A.html

I have the changes in feature/remote-name-decoded branch here: 

https://github.com/magks/curl/tree/feature/remote-name-decoded

I tried to keep changes as minimal and simple as possible and made use of the lib/escape.h  `Curl_urldecode` function, however because of this, the linker can only find the symbol when I pass  `--disable-symbol-hiding` to ./configure.

I wanted to discuss with you what approach you'd recommend taking to include the function from escape.h in tool_operhlp.c and tool_cb_wrt.c