lua dkjson: use us_tostring() to fix locale issues with decimals
lua dkjson: use us_tostring() to fix locale issues with decimals

This only fixes encoding but we don't use decoding anyway.

Fixes #8854

shyamalschandra/vlc,shyamalschandra/vlc,krichter722/vlc,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,shyamalschandra/vlc,shyamalschandra/vlc,xkfz007/vlc,vlc-mirror/vlc,jomanmuk/vlc-2.2,xkfz007/vlc,xkfz007/vlc,vlc-mirror/vlc,krichter722/vlc,xkfz007/vlc,jomanmuk/vlc-2.2,xkfz007/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc,shyamalschandra/vlc,xkfz007/vlc,krichter722/vlc,vlc-mirror/vlc,krichter722/vlc,shyamalschandra/vlc,krichter722/vlc,shyamalschandra/vlc,vlc-mirror/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc,xkfz007/vlc,krichter722/vlc,krichter722/vlc,vlc-mirror/vlc