Revert "fixed linker error regarding IRQ handlers"

This reverts commit 1bd3a75e52236ab5d0591dcd44ea8f14c84da6f7.
fixed LD err about IRQ handlers (recommit)
added uart single wire half duplex mode, bidir mode
fixed permanent occupation of serial port

a small bug made it impossible to change port functions during run time
implemented smartport

not heavily tested
lightly tested binary with smartport