Installation instructions for DEC OSF1 V5.x

Installation on DEC (now Compaq) OSF1 succeeded mostly for compilation with both gcc2.95 and cxx version 6.3. Some issues remain:

To use one or the other compiler, you have to set the CXX environment variable to either g++ or cxx. If it is not set, the configuration scripts seems to take g++ as compiler. Please also set the CC environment variable to a corresponding C compiler.