libcppa: 0.7.1 - Actor Model implementation for C++11

Adding a new library.

libcppa: 0.7.1 - Fixed formula

Fixed formula requirements.

libcppa: 0.7.1 - Fixing

libcppa: 0.7.1 - Disabling context switch option

libcppa: 0.7.1 - Requires C++11 capable compiler

Update libcppa.rb

libcppa: 0.7.1 - Removing build numbers

libcppa: 0.7.1 - Build fails with Snow Leopard

Update libcppa.rb

Update libcppa.rb

Update libcppa to version 0.8.1