Makefile: configurable narcissus, don't mess with ~/.profile

[clausreinke]

• With narcissus now a proper submodule, it can be useful to take sources for make install from an existing repo.
• keep make install from messing with ~/.profile: it isn't nice, it does not achieve the purpose of setting an environment variable (eg, when running node from a shell that doesn't process ~/.profile), it might overwrite existing .profile.bak, ..

patch is here.

This might need further refinement, eg when NODE_PATH is empty, setting it to "somepath:" isn't quite right. But that is now just a message, so it is an improvement.