Support name mangling in C++ and Vala symbol filters

[Robert Ancell]

In C the symbol filter is easy (maps to function names)

libraries.test1
{
    sources = lib.c
    symbol-filter = foo bar
}

In C++ and Vala the symbol names are a bit more complex, we should be able to specify (as much as possible) native symbols in the filter list, i.e.

libraries.test2
{
    sources = lib.cpp
    symbol-filter = namespace::Class::method
}

libraries.test3
{
    sources = lib.vala
    symbol-filter = Namespace.Class.method
}