Autoindex: escape '?' in file names.

For files with '?' in their names autoindex generated links with '?' not
escaped.  This resulted in effectively truncated links as '?' indicates
query string start.

This is an updated version of the patch originally posted at [1].  It
introduces generic NGX_ESCAPE_URI_COMPONENT which escapes everything but
unreserved characters as per RFC 3986.  This approach also renders unneeded
special colon processing (as colon is percent-encoded now), it's dropped
accordingly.

[1] http://nginx.org/pipermail/nginx-devel/2010-February/000112.html

Reported by Konstantin Leonov.
diff --git a/src/core/ngx_string.c b/src/core/ngx_string.c
index 75bc657..8f29e90 100644
--- a/src/core/ngx_string.c
+++ b/src/core/ngx_string.c
@@ -1380,6 +1380,26 @@
         0xffffffff  /* 1111 1111 1111 1111  1111 1111 1111 1111 */
     };
 
+                    /* not ALPHA, DIGIT, "-", ".", "_", "~" */
+
+    static uint32_t   uri_component[] = {
+        0xffffffff, /* 1111 1111 1111 1111  1111 1111 1111 1111 */
+
+                    /* ?>=< ;:98 7654 3210  /.-, +*)( '&%$ #"!  */
+        0xfc009fff, /* 1111 1100 0000 0000  1001 1111 1111 1111 */
+
+                    /* _^]\ [ZYX WVUT SRQP  ONML KJIH GFED CBA@ */
+        0x78000001, /* 0111 1000 0000 0000  0000 0000 0000 0001 */
+
+                    /*  ~}| {zyx wvut srqp  onml kjih gfed cba` */
+        0xb8000001, /* 1011 1000 0000 0000  0000 0000 0000 0001 */
+
+        0xffffffff, /* 1111 1111 1111 1111  1111 1111 1111 1111 */
+        0xffffffff, /* 1111 1111 1111 1111  1111 1111 1111 1111 */
+        0xffffffff, /* 1111 1111 1111 1111  1111 1111 1111 1111 */
+        0xffffffff  /* 1111 1111 1111 1111  1111 1111 1111 1111 */
+    };
+
                     /* " ", "#", """, "%", "'", %00-%1F, %7F-%FF */
 
     static uint32_t   html[] = {
@@ -1443,7 +1463,7 @@
                     /* mail_auth is the same as memcached */
 
     static uint32_t  *map[] =
-        { uri, args, html, refresh, memcached, memcached };
+        { uri, args, uri_component, html, refresh, memcached, memcached };
 
 
     escape = map[type];