Bug 1005321 - Convert the xpt code to C++; r=bholley

--HG--
rename : xpcom/typelib/xpt/src/xpt_arena.c => xpcom/typelib/xpt/src/xpt_arena.cpp
rename : xpcom/typelib/xpt/src/xpt_struct.c => xpcom/typelib/xpt/src/xpt_struct.cpp
rename : xpcom/typelib/xpt/src/xpt_xdr.c => xpcom/typelib/xpt/src/xpt_xdr.cpp
rename : xpcom/typelib/xpt/tests/PrimitiveTest.c => xpcom/typelib/xpt/tests/PrimitiveTest.cpp
rename : xpcom/typelib/xpt/tests/SimpleTypeLib.c => xpcom/typelib/xpt/tests/SimpleTypeLib.cpp