Return result codes from step/wait/loop callbacks. #55

Job	Run time
FreeBSD (Default)	2m 10s
Emscripten (Default)	40s
Android (armeabi-v7a, Default)	1m 36s
NetBSD (Default)	3m 36s
macOS (No Device IO)	40s
Android (arm64-v8a, Default)	1m 23s
macOS (Force C++)	38s
macOS (Default)	38s
Windows (msvc, Default)	55s
macOS (Force C89)	28s
OpenBSD (Default)	3m 30s
Linux (gcc, Default)	1m 1s
Windows (msvc, No Device IO)	1m 19s
Android (x86_64, Default)	58s
Windows (msvc, Force C++)	1m 8s
Additional Configurations (No SSE2)	53s
Additional Configurations (No Encoding)	52s
Additional Configurations (No Decoding)	50s
Windows (mingw, Default)	2m 44s
Windows (mingw, Force C++)	2m 42s
Linux (clang, Force C89)	48s
Linux (gcc, Force C89)	56s
Windows (mingw, No Device IO)	3m 5s
Linux (clang, No Device IO)	57s
Linux (gcc, No Device IO)	1m 2s
Additional Configurations (No Threading)	45s
Linux (clang, Force C++)	1m 0s
Linux (gcc, Force C++)	1m 2s
Linux (clang, Default)	52s
	39m 8s

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