liblog: logcat: add epoch and monotonic format modifiers

- '-v epoch' prints seconds since Jan 1 1970
- '-v monotonic' print cpu seconds since start of device
- '-T sssss.mmm...' as alternate tail time format

NB: monotonic is a best estimate and may be out by a few ms
    given the synchronization source clue accuracy.

Bug: 23668800
Change-Id: Ieb924b6d3817669c7e53beb9c970fb626eaad460
diff --git a/include/log/logprint.h b/include/log/logprint.h
index 26b1ee5..204b3f2 100644
--- a/include/log/logprint.h
+++ b/include/log/logprint.h
@@ -42,6 +42,8 @@
     FORMAT_MODIFIER_PRINTABLE, /* converts non-printable to printable escapes */
     FORMAT_MODIFIER_YEAR,      /* Adds year to date */
     FORMAT_MODIFIER_ZONE,      /* Adds zone to date */
+    FORMAT_MODIFIER_EPOCH,     /* Print time as seconds since Jan 1 1970 */
+    FORMAT_MODIFIER_MONOTONIC, /* Print cpu time as seconds since start */
 } AndroidLogPrintFormat;
 
 typedef struct AndroidLogFormat_t AndroidLogFormat;