Merge branch 'pw/maint-p4-rcs-expansion-newline'

I do not have p4 to play with, but looks obviously correct to me.

* pw/maint-p4-rcs-expansion-newline:
  git p4: RCS expansion should not span newlines

diff --cc git-p4.py
Simple merge

diff --cc t/t9810-git-p4-rcs.sh
Simple merge