plist_to_xml: use POSIX locale to make sure '.' is used for floats
plist_to_xml: use POSIX locale to make sure '.' is used for floats

In locales like German, a ',' is used as a decimal separator. When the
program calling plist_to_xml uses LC_NUMBER with something different
than a '.', parsing of the resulting XML document fails. This patch
fixes it.

Tatsh/libplist,libimobiledevice/libplist,Tatsh/libplist,libimobiledevice-win32/libplist,libimobiledevice-win32/libplist,libimobiledevice/libplist,libimobiledevice-win32/libplist,libimobiledevice/libplist,Tatsh/libplist,Tatsh/libplist,libimobiledevice-win32/libplist