STYLE: simplify/shorten some token names

src/OpenFOAM/db/IOstreams/Pstreams/UIPstream.C

src/OpenFOAM/db/IOstreams/Pstreams/UOPstream.C

src/OpenFOAM/db/IOstreams/Sstreams/ISstream.C

src/OpenFOAM/db/IOstreams/Sstreams/OSstream.C

src/OpenFOAM/db/IOstreams/Sstreams/prefixOSstream.C

src/OpenFOAM/db/IOstreams/token/token.H

src/OpenFOAM/db/IOstreams/token/tokenI.H

src/OpenFOAM/db/IOstreams/token/tokenIO.C

...nFOAM/db/dictionary/functionEntries/ifeqEntry/ifeqEntry.C