Support proxy authentication

[quicklisp]

Add support for HTTP proxies that require authentication. See http://groups.google.com/group/quicklisp/browse_thread/thread/aba32c79d80eec86 for the initial request.

[quicklisp]

Also, this support should carry over into quicklisp-client.

[hajovonta]

This is a very old issue. Is there any progress?

[quicklisp]

http://netprophetblog.blogspot.com/2014/02/tool-posting-quicklisp-with.html is what I recommend right now.

[informatimago]

[6]> (quicklisp-quickstart:install :proxy "http://bourguignonp:xxxxxxxxxxxx@10.253.35.2:3128/")
; Fetching #<URL "http://beta.quicklisp.org/client/quicklisp.sexp">
; 0.82KB
==================================================
838 bytes in 0.02 seconds (40.40KB/sec)
; Fetching #<URL "http://beta.quicklisp.org/client/2017-03-06/quicklisp.tar">
; 250.00KB
==================================================
256,000 bytes in 0.03 seconds (9650.27KB/sec)
; Fetching #<URL "http://beta.quicklisp.org/client/2015-09-24/setup.lisp">
; 4.94KB
==================================================
5,054 bytes in 0.00 seconds (2264.01KB/sec)
; Fetching #<URL "http://beta.quicklisp.org/asdf/2.26/asdf.lisp">
; 194.07KB
==================================================
198,729 bytes in 0.11 seconds (1729.21KB/sec)
*** - Bad port in URL "http://bourguignonp:xxxxxxxxxxxx@10.253.35.2:3128/"
The following restarts are available:
SKIP           :R1      skip (SETUP)
RETRY          :R2      retry (SETUP)
STOP           :R3      stop loading file /home/pjb/quicklisp/setup.lisp
ABORT          :R4      Abort main loop
Break 1 QL-SETUP[7]> 

Congratulations. You corrected (kludged would be a better word IMO) the parsing of URIs in quicklisp.lisp, but forgot to do the same everywhere else...