Build in C++11 mode
Switch to std::shared_ptr or std::unique_ptr

Additional use of std::unique_ptr is possible, but will require
additional review and perhaps refactoring.
Use "= delete"
cxxll::url_source: Make moveable
download(): Use move support in url_source
cxxll::task: Add move support
Use cxxll::task move support in test cases
Introduce std::make_shared in a few places
cxxll::expat_source::state_type: Switch to scoped enum
cxxll::elf_image::dynamic_section_range::kind: Switch to scoped enum
cxxll::asdl::cardinality: Switch to scoped enum
cxxll::hash_algorithm: Renamed from cxxll::hash_sink::type

This is type is now a scoped enum.
cxxll::java_class: Remove unused enum constants
cxxll::mmap_handle::munmap(): New member function
cxxll::mmap_handle::read_only(): New member function

Replace the existing constructor with move support.
cxxll::pg_query: Use variadic templates for outer dispatch
cxxll::pg_response: Use variadic templates
cxxll::pg_query: Use out-of-line constant array for parameter formats
cxxll::pg_query: Use out-of-line constant for parameter OIDs
cxxll::pg_query: Use variadic templates for code generation