Fix missing type encoding case for long double.

This was triggered when upgrading ivars from the pre-2.0 ABI that used
long double - their alignment could not be calculated correctly and we
hit an assertion.

Fixes: #82

type_encoding_cases.h

@@ -8,6 +8,7 @@
 #ifndef APPLY_TYPE
 #error Define APPLY_TYPE(type, name, capitalizedName, encodingChar) before including this file
 #endif
+APPLY_TYPE(long double, long double, LongDouble, 'D')
 APPLY_TYPE(double, double, Double, 'd')
 APPLY_TYPE(float, float, Float, 'f')
 APPLY_TYPE(signed char, char, Char, 'c')