Remove Zygote.fork

Currently unused, all callers use forkAndSpecialize.

Change-Id: I61df8ed88d7657da8280e044fe99517c47ce8dff
Remove Zygote.systemInSafeMode.

This field has moved to the SystemServer class.

Change-Id: Ia66340dd934e6ec62a72e3641085602cb9f252f5
Merge "Remove Zygote.fork"
Merge "Remove Zygote.systemInSafeMode."
Fix a copy and paste doc error

Change-Id: I2a142f0a6e8348993b37666876d4f812a7e69986
Merge "Fix a copy and paste doc error"