Several packages rely on the C pre-processor (xrdb among
others). This package normally comes with the C compiler
such as gcc. Sadly, in RedHat 5.2 only egcs provides
/lib/cpp so that if you only install gcc, you won't get
/lib/cpp nor any cpp manual.
It seems that the conflict between egcs's cpp and gcc's cpp
could be resolved in the same way as the conflict between
csh's /bin/csh and tcsh's /bin/csh allowing both gcc and
egcs to provide /lib/cpp and cpp's manual.
this is fixed in 5.9+ by having a separate cpp package.