localeToCharset:
Select a Suitable Encoding Name from a Locale Name
Description
This functions aims to find a suitable coding for the locale named, by
default the current locale, and if it is a UTF-8 locale a suitable
single-byte encoding.
A character vector naming an encoding and possibly a fallback
single-encoding, NA if unknown.
Details
The operation differs by OS.
windows
A Windows locale is specified like "English_United Kingdom.1252".
The final component gives the codepage, and this defines the encoding.
unix
Locale names are normally like es_MX.iso88591. If final
component indicates an encoding and it is not utf8 we just need
to look up the equivalent encoding name. Otherwise, the language
(here es) is used to choose a primary or fallback encoding.