Reset value of TEXTDOMAIN locally to common functions.
- Previously, common functions didn't reset the TEXTDOMAIN environment
variable. This made gettext to read the MO file set in the last
TEXTDOMAIN definition which may not include the translated strings
for the function in turn. This update changes the common functions
that make calls to gettext in order to reset the value of TEXTDOMAIN
environment variable locally to the appropriate package.
Because the TEXTDOMAIN variable is reset locally to common
functions, the value it has on higher scopes isn't affected by this
local reset. This way, it is possible to separate localization of
modules from localization of common functions.