proxy: allow socks:// prefix in proxy string

Inspired by a patch from OB.Conseil. Added test case 708 to verify.

tests/data/Makefile.am

@@ -71,7 +71,8 @@ EXTRA_DIST = test1 test108 test117 test127 test20 test27 test34 test46	   \
  test1203 test1117 test1118 test1119 test1120 test1300 test1301 test1302 \
  test1303 test320 test321 test322 test323 test324 test1121 test581 test580 \
  test1304 test1305 test1306 test1307 test582 test583 test808 test809       \
- test810 test811 test812 test813 test584 test1122 test1123 test1124 test1125
+ test810 test811 test812 test813 test584 test1122 test1123 test1124 test1125 \
+ test708
 
 filecheck:
 	@mkdir test-place; \

tests/data/test708

@@ -0,0 +1,60 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP GET
+SOCKS4
+</keywords>
+</info>
+
+#
+# Server-side
+<reply name="1">
+<data>
+HTTP/1.1 200 OK
+Date: Thu, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Last-Modified: Tue, 13 Jun 2000 12:10:00 GMT
+ETag: "21025-dc7-39462498"
+Accept-Ranges: bytes
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+Funny-head: yesyes
+
+-foo-
+</data>
+</reply>
+
+#
+# Client-side
+<client>
+<server>
+http
+socks4
+</server>
+<setenv>
+all_proxy=socks4://%HOSTIP:%SOCKSPORT
+</setenv>
+ <name>
+HTTP GET via SOCKS4 proxy
+ </name>
+ <command>
+http://%HOSTIP:%HTTPPORT/708
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<strip>
+^User-Agent:.*
+</strip>
+<protocol>
+GET /708 HTTP/1.1
+Host: %HOSTIP:%HTTPPORT
+Accept: */*
+
+</protocol>
+</verify>
+</testcase>