boot: methods (fn T.m, self by address, mutation analysis), str() of any value

Methods are functions whose first parameter is the receiver's address; a method
that changes self can't be called on a temporary or a read-only value, and
calling one on a variable keeps a parameter from being borrowed. An argument
that lives inside the receiver is copied (c.merge(c)). str(x) and print of
arrays and structs go through one formatter, as in the C++ compiler.

boot.sh: 12 passed, 0 failed, 10 skipped.

boot/parser.fch

@@ -195,6 +195,10 @@ fn parseFn(ptr[Parser] p) -> ast.Node {
     f := node(p, "fn")
     expect(p, "fn", "'fn', 'struct' or 'import'")
     f.name = expect(p, "ident", "a function name").text
+    if accept(p, ".") {
+        f.recv = f.name
+        f.name = expect(p, "ident", "a method name").text
+    }
     expect(p, "(", "'('")
     p.depth += 1
     if !at(p, ")") {