Use unsigned types everywhere to be compatible with the standard, which is more restrictive in this respect.

[SVN r68823]

libs/random

@@ -1 +1 @@
-Subproject commit 8c30753bf49504b5f677b8b410a3787907c86bd0
+Subproject commit e4cca265d0ff13c0fd1bc5bee132d0342195fa66