preprocessor to run. Previously, it always ran /usr/bin/cpp, unless you
used the -Y option, and even then you could not set the basename. It
also attempted to run /usr/ccs/lib/cpp for SVR4 compatibility, but this
is obsolete, and has been removed.
Note that setting RPCGEN_CPP to a command with arguments is supported,
though the command line parsing is simplistic. However, setting it to
e.g. "gcc46 -E" or "clang -E" will lead to problems, because both gcc
and clang in -E mode will consider files with unknown extensions (such
as .x) as object files, and attempt to link them.
This could be worked around by also adding "-x c", but it is much safer
to set RPCGEN_CPP to e.g. "cpp46" or "clang-cpp" instead.
MFC after: 1 week