Make hgweb.staticfile() more secure and portable. Without this, files in directories next to the static directory starting with 'static' could be retrieved, e.g. with '../static.private/foo'. Additionally staticfile now generates platform specific pathnames from the /-separated paths given in the URL. Illegal file names (e.g. containing %00) now yield a sane error message.

adding foo
adding bomb
adding a.c
adding dir/a.o
adding dir/b.o
! a.c
! dir/a.o
! dir/b.o
? .hgignore
a.c: unsupported file type (type is fifo)
! a.c