dotdot: introducing dot file path cleanup

RFC3986 details how a path part passed in as part of a URI should be
"cleaned" from dot sequences before getting used. The described
algorithm is now implemented in lib/dotdot.c with the accompanied test
case in test 1395.

Bug: http://curl.haxx.se/bug/view.cgi?id=1200
Reported-by: Alex Vinnik

tests/data/test1395

@@ -0,0 +1,26 @@
+<testcase>
+<info>
+<keywords>
+unittest
+</keywords>
+</info>
+
+#
+# Client-side
+<client>
+<server>
+none
+</server>
+<features>
+unittest
+</features>
+ <name>
+Curl_dedotdotify
+ </name>
+<tool>
+unit1395
+</tool>
+
+</client>
+
+</testcase>