1. ifu: redirect npc only when if2 or if4 fire
2. ifu: set if2_valid false when if4 redirect
3. bpu: block stage1 when stage2 is not ready
4. ibuffer: add logs

IBuffer: Make verilog optimize, cputest passed

BPU PerfCnt: move to CSR

Fix temp lsu

ifu: fix pnpc of fetchPacket

scripts: add a line-count statistic script

Fix boringutils bug by adjust the instantiation order of the front and back ends

brq: do not use anonymous signals in boringutils

EMU: print seed value before return

Uart: print to stdout

Log buffer

* this helps to seperate the message printed by emu from the logs in
  chisel

* printf() in chisel will finally output to stderr. Using a buffer will
  improve performance while redirecting stderr to a file.
* If log is enabled for every cycle, this can speed up 2X for simulation.

Impl floating point load/store