Adopt Nls PSR-4

[ralflang]

Nls is used in Horde_Core_Form_Type_Number::isValid - Use Horde\Nls\Nls::getLocaleInfo() instead
Nls is used in Horde_Form_VarRenderer_Xhtml::_renderVarDisplay_number - Use Horde\Nls\Nls::getLocaleInfo() instead

See https://github.com/horde/Nls/blob/FRAMEWORK_6_0/doc/UPGRADING.md