[NL] Extrp; Change initialization of CachedData.

From the standard: If the initializer list has no elements and T is
a class type with a default ctor, the object is value-initialized.

The warning appearing in gcc-4.9 is due to a c++11 defect
fixed in
http://open-std.org/JTC1/SC22/WG21/docs/cwg_defects.html#1324
which points to
http://open-std.org/JTC1/SC22/WG21/docs/cwg_defects.html#1301.

The warning is fixed in later versions of gcc:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55805