TwoPunctures contains globally visible symbols not prefixed by thorn name

[Roland Haas]

TwoPunctures contains a number of functions (and possibly global variables) that are not prefixed by the thorn name and thus cause name clashes.

This is most obvious when one compares the derived codes TwoPunctures_BBHSF and TwoPunctures_KerrProca to TwoPunctures (eg using diff -ur) since the derived codes already added the prefixes.

This should however also be fixed in TwoPunctures since some of the names are very generic (eg Index() and interpol).