tests: test-check-code-hg.t works for all files to check with xargs, backslashes are eaten up. Convert them to slashes therefore. This is only a problem with ls (on windows). hg manifest returns slashes. The pipe char is moved before the line end for telling check-code.py that sed does not modify the output.

check-code: do not abort on an unreadable file, only report this

heads: fix children/descendants in doc (issue3992)

paper: fix rendering of the first tab in a line in Webkit (issue3990) This fixes issue3990 for Webkit-browsers, and also older Opera versions. Rendering in firefox is not changed.