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Jim Brunner authoredUpdate adds a general source for retrieving a monotonic time. In addition, AE has been updated to utilize the new monotonic clock for timer processing. This performance improvement is **not** enabled in a default build due to various H/W compatibility concerns, see README.md for details. It does however change the default use of gettimeofday with clock_gettime and somewhat improves performance. This update provides the following 1. An interface for retrieving a monotonic clock. getMonotonicUs returns a uint64_t (aka monotime) with the number of micro-seconds from an arbitrary point. No more messing with tv_sec/tv_usec. Simple routines are provided for measuring elapsed milli-seconds or elapsed micro-seconds (the most common use case for a monotonic timer). No worries about time moving backwards. 2. High-speed assembler implementation for x86 and ARM. The standard method for retrieving the monotonic clock is POSIX.1b (1993): cloc... c01e94a4