Mention of make install for amuleweb #864

Came across this string in the gettext catalogs:
You requested to run web server on startup, but the amuleweb binary cannot be run. Please install the package containing aMule web server, or compile aMule using --enable-webserver and run make install. The original string seems to live in src/amule.cpp.

This compilation instruction is probably outdated as aMule switched to CMake, so an update may be useful.