Make a new object called Fixer to hold the state of the tree, and
make a copy of the input tree so the original doesn't get modified.
Test: bpfix_test.go
Change-Id: I1dc6fd99158c8b0e1db029df99e6cf72699a5e63
The functions in bpfix that take a *parser.List and return a
modified *parser.List are always returning the same pointer
and mutating the target of the pointer. Remove the extra
unnecessary return value.
Also extract the getLiteralListProperty function.
Test: androidmk_test.go
Change-Id: I08d8aff955c72b7916741cda8083974a49af4d6f
