rply: Guard against locales with different decimal point separators
rply: Guard against locales with different decimal point separators

rply was using strtod and printf with "%g" which would mean that the
format of the PLY files would depend on the locale. This fixes it to
use g_ascii_strtod and g_ascii_formatd so that the decimal point will
be corrected to consistently use '.' as the separator.

eliasbakken/mash,eliasbakken/mash,clutter-project/mash,clutter-project/mash,clutter-project/mash