Cleaning legacy commands in protobuf spec file.

Signed-off-by: Salvatore Di Guida <salvatore.di.guida@cern.ch>
Run the clean section only for EL5: deprecated as for rpm >= 4.8.0, as in EL6.

Signed-off-by: Salvatore Di Guida <salvatore.di.guida@cern.ch>
Improved documentation for reference, source files and rpmlint.

Signed-off-by: Salvatore Di Guida <salvatore.di.guida@cern.ch>
Adding steps for building RPM in EL5.

Signed-off-by: Salvatore Di Guida <salvatore.di.guida@cern.ch>
Style changes in protobuf README.

Signed-off-by: Salvatore Di Guida <salvatore.di.guida@cern.ch>