estimate clocks modified SoftwareSerial.cpp results

cc calc.c
uaa@framboise:~$ ./a.out
16000000    300 53320(0) 26612(24) 53320(8) 39964(16)
16000000    600 26652(0) 13280(24) 26652(8) 19964(16)
16000000   1200 13320(0)  6612(24) 13320(8)  9964(16)
16000000   2400  6652(0)  3280(24)  6652(8)  4964(16)
16000000   4800  3320(0)  1612(24)  3320(8)  2464(16)
16000000   9600  1652(0)   780(24)  1652(8)  1216(16)
16000000  19200   820(0)   364(24)   820(8)   592(16)
16000000  38400   404(0)   156(24)   404(8)   280(16)
16000000  57600   264(0)    84(24)   264(8)   172(16)
16000000 115200   124(0)    16(12)   124(8)    68(16)
16000000 230400    56(0)     4(0)    56(8)    16(12)
uaa@framboise:~$

no difference about tranmit
_rx_delay_centering +6 or +3 ticks (+24 or +12 CPU clocks)
_rx_delay_intrabit +2 ticks (+8 CPU clocks)
_rx_delay_stopbit +4 or +3 ticks (+16 or +12 CPU clocks)