(lang/R-cpp11)  Updated 0.3.1 to 0.4.2

# cpp11 0.4.2

* Romain Fran巽ois is now the maintainer.

# cpp11 0.4.1

* Fix crash related to unwind protect optimization (#244)

# cpp11 0.4.0

## New Features

* New  opt-in  message  formatting  with the  {fmt}  C++  library  for
  `cpp11::messages()` `cpp11::stop()` and `cpp11::warning()`.  Set the
  `CPP11_USE_FMT`    macro  to    use    this    feature  in    your
  package. (@sbearrows, #169, #208)

* New `as_double()` and `as_integer()` methods to coerce integers to
  doubles and doubles to integers to doubles (@sbearrows, #46)

* `cpp11::matrix` iterators can now be used either row-wise or
  column-wise (the default) depending on the user's choice (@alyst,
  #229)

## Improvements and fixes

* Read-only matrix accessors are now marked const (#234)

* `writable::r_vector` default constructors now return a 0 length
  vector when converted to `SEXP` (#166)

* Read-only `r_vector` constructors now disallow implicit construction
  with named arguments (#237)

* Read-only `r_vector.attr()` methods now return const objects, so it
  is a compile time error to try to assign to them (#237)

* Fixed `+` and `+=` operators of `r_vector::[const_]iterator` to
  conform the *iterators* concept: `+=` updates the iterator, and `+`
  returns the updated copy, while keeping the original unchanged
  (@alyst, #231)

* Remove undefined behavior when constructing global `cpp11::sexp`s (#224)

* Removed redundant `.Call calls` in cpp11.cpp file (@sbearrows, #170)

* Error messages now output original file name rather than the
  temporary file name (@sbearrows, #194)

* `cpp_register()` now includes `attribute_visible` in the init
  function, so packages compiled with `C_VISIBILITY` will find the
  init function.

* Fixed bug when running `cpp_source()` on the same file more than
  once (@sbearrows, #202)

* Allow cpp11 decorators of the form `cpp11::linking_to` (@sbearrows,
  #193)

* Removed internal instances of `cpp11::stop()` and replaced with C++
  exceptions (@sbearrows, #203)

* Names of named lists are now resized along with the list elements
  (@sbearrows, #206)

(mef)