merkle: improve the speed of p_key_in_I by 20%
merkle: improve the speed of p_key_in_I by 20%

-> improves the speed of keys_to_intervals/2
tectronics/scalaris,seyyed/scalaris,tectronics/scalaris,tectronics/scalaris,digshock/scalaris,seyyed/scalaris,seyyed/scalaris,seyyed/scalaris,tectronics/scalaris,digshock/scalaris,tectronics/scalaris,seyyed/scalaris,digshock/scalaris,digshock/scalaris,digshock/scalaris,tectronics/scalaris,digshock/scalaris,seyyed/scalaris,seyyed/scalaris,digshock/scalaris,tectronics/scalaris