Log Message:
(math/R-backports) Updated 1.1.4 to 1.2.1

# backports 1.2.1

* Adapted `get0()` to work with R-devel / R-4.1.0 for first argument having \ 
length greater than 1.

# backports 1.2.0

* Switched to semantic versioning.
* Added backport for `asplit()` for R versions prior to 3.6.0 (#47).
* Added backport for `removeSource()` which also supports language objects for R \ 
versions prior to 3.6.0 (#50).
* Added backport for `isNamespaceLoaded` for R versions prior to 3.2.0 (#49).

# backports 1.1.10
* Added `suppressMessages()` and `suppressWarnings()` with support for argument \ 
`classes` for R versions prior to 4.0.0

# backports 1.1.9
* Added backports for `str2lang()` and `str2expression()` (#42)
  Thanks to @dmurdoch.
* `import()` imported too many functions and has been fixed.

# backports 1.1.8
* Added backport for `tools::vignetteInfo()` for R versions prior to 3.6.0
* Fixed import of `list2DF()` and `deparse1()`

# backports 1.1.7
* Added backport for `deparse1()` for R versions prior to 4.0.0.
* Added backport for `list2DF()` for R versions prior to 4.0.0.

# backports 1.1.6
* Added backport for `R_user_dir()` for R versions prior to 4.0.0.
* Added `dQuote()` and `sQuote()` with support for argument `q` for R versions \ 
prior to 3.6.0.

# backports 1.1.5
* Changed license from GPL-2 to GPL-2 or GPL-3.
* Added backport for `isTRUE()` implementing the new behaviour introduced in R 3.5.0.