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

(cherry picked from commit 4316ff068b14eff72d3adecd432a602a453db95d)
Signed-off-by: Pierre Ynard <efc674bf215af8c633f25041b289869f9d3ac058@yahoo.fr>

vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,vlc-mirror/vlc-2.1,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,jomanmuk/vlc-2.1,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1