Add extra check for Floating-Point Unit (__VFP_FP__) when compiling for arm in pack/unpack conditional used in 'double' type case. This is a special case when neither fpu or arm-eabi is present (arm-oabi).

This fixes 'double' related bug in iOS devices (armv6, armv7, armv7s) caused by running the arm-oabi endianess alignment code.