logd: replace internal CLOCK_MONOTONIC use with sequence numbers

- switch to simpler and faster internal sequence number, drops
  a syscall overhead on 32-bit platforms.
- add ability to break-out of flushTo loop with filter return -1
  allowing in reduction in reader overhead.

Change-Id: Ic5cb2b9afa4d9470153971fc9197b07279e2b79d
diff --git a/logd/FlushCommand.cpp b/logd/FlushCommand.cpp
index 3be07c0..26a1861 100644
--- a/logd/FlushCommand.cpp
+++ b/logd/FlushCommand.cpp
@@ -27,7 +27,7 @@
                            unsigned long tail,
                            unsigned int logMask,
                            pid_t pid,
-                           log_time start)
+                           uint64_t start)
         : mReader(reader)
         , mNonBlock(nonBlock)
         , mTail(tail)