fix compiler error: change leap_second_scheduled from const struct time_data_t using a pointer
fix compiler crash: remove __attribute__((always_inline)) from function days_per_month()
update commit 901b8c3: remove changing a constant using a pointer

possible solution: tell verify_leap_second_scheduled() with an additional parameter
to assume a leap_second instead of temporarily overwriting leap_second_scheduled variable
in a const struct.
minor cosmetics
Merge branch 'chris-est-arduino_1.5.8_beta_fixup'