libdfp: Add issignaling test to new framework
libdfp: Remove converted tests
libdfp: Add FP_LLOGB0 and FP_LLOGBNAN return codes

This patch add the two definitions if they are not already defined in
system libraries. It also change llogb to return FP_LLOGB0 in case of 0
input and FP_LLOGBNAN in case of NaN.
libdfp: Add long int type to gen-libdfp-tests.py
libdpf: Adapt ilogb/llogb tests for new framework
libdfp: Add gen-libdfp-test DEC_MIN_EXP_SUB and fix values
libdfp: Fix llquantemp subnormal representation
libdfp: Adapt quantum testcase for new framework
libdpf: Adapt rounding tests to new framework