use the absolute value to check the test result against an epsilon
add a testcase, that on ARM hardfloat needs more than the 8  VFP argument registers to pass arguments to a call
extract code to align the argument storage pointer to a helper function
extract setting of arguments to be passed to a helper function
move the hardfloat specific argument copying code to the helper function
separate ARM ffi_prepare_args in a version implementing the simple SYSV calling convention and one for the hard-float calling convention
extend ffi_prepare_args for FFI_VFP (hard-float ABI), fixing an issue with passing VFP arguments in VFP registers and the stack, while at the same time not using all core registers.
add a failing test for closures on ARM hardfloat
create separated versions of ffi_prep_incoming_args_* for SYSV and VFP ABIs.

The different versions will be called depending on the value of cif->abi
folow the ARM hard-float ABI in ffi_prep_incoming_args_VFP