check_environment: Check whether a string corresponds to the name of an...
In envnames: Keep Track of User-Defined Environment Names

The input string is checked as a valid environment name. The environment can be a named environment (system or package) or a user environment.

1	check_environment(x, envir)

`x`	string to evaluate that may represent an environment
`envir`	environment where `x` should be evaluated first. If it is not found there it still searched for in the whole workspace.

A list with two elements:

found whether the string contained in x is the name of an existing environment in the workspace
env_name the name of the environment (after stripping out any system environments such as globalenv(), baseenv() or a package environment) (for instance "globalenv()$env$env1" is returned as "env$env1"), or NULL if no environment was found corresponding to the name given in x.