[core] preserve PATH_INFO case on case-insensitive fs (fixes #406)

attempt to preserve PATH_INFO case even when the
URI is mapped onto a case-insensitive file system.

NTFS (Windows) is case-insensitive (even though it is case-preserving)
HFS+ (Mac OS X) can be formatted to be case-insensitive

x-ref:
  "... PATH_INFO ... improperly converted to lowercase"
  https://redmine.lighttpd.net/issues/406

src/response.c

@@ -696,13 +696,24 @@ handler_t http_response_prepare(server *srv, connection *con) {
 
 			/* we have a PATHINFO */
 			if (pathinfo) {
-				buffer_copy_string(con->request.pathinfo, pathinfo);
+				size_t len = strlen(pathinfo), reqlen;
+				if (con->conf.force_lowercase_filenames
+				    && len <= (reqlen = buffer_string_length(con->request.uri))
+				    && 0 == strncasecmp(con->request.uri->ptr + reqlen - len, pathinfo, len)) {
+					/* attempt to preserve case-insensitive PATH_INFO
+					 * (works in common case where mod_alias, mod_magnet, and other modules
+					 *  have not modified the PATH_INFO portion of request URI, or did so
+					 *  with exactly the PATH_INFO desired) */
+					buffer_copy_string_len(con->request.pathinfo, con->request.uri->ptr + reqlen - len, len);
+				} else {
+					buffer_copy_string_len(con->request.pathinfo, pathinfo, len);
+				}
 
 				/*
 				 * shorten uri.path
 				 */
 
-				buffer_string_set_length(con->uri.path, buffer_string_length(con->uri.path) - strlen(pathinfo));
+				buffer_string_set_length(con->uri.path, buffer_string_length(con->uri.path) - len);
 			}
 
 			if (con->conf.log_request_handling) {