package_rpm.bbclass : escape "%" in files and directories name
The rpm process replace all the "%name" in the spec file by the name of
the package. So, if the package is composed of some files or directories
named "%name...", the rpm package process failed.
Replace all "%" present in files or directories names by "%%%%%%%%" to
correctly escape "%" due to the number of times that % is treated as an
escape character. Jeff Johnson says this is the Right Thing To Do.
