Update VERSIONs to 3.7-rc2 for release. #19

Job	Run time
build (gcc, 3.12, 3.3)	1m 35s
build (gcc, 3.12, 3.3, test-flags-override)	1m 20s
build (gcc, 3.12, 3.3, test-debug)	1m 31s
build (gcc, 3.12, 3.3, linker-bfd)	1m 37s
build (gcc, 3.12, 3.3, linker-gold)	1m 40s
build (gcc, 3.11, 3.3)	1m 29s
build (gcc, 3.10, 3.3)	1m 44s
build (gcc, 3.9, 3.3)	1m 34s
build (gcc, 3.8, 3.3)	1m 35s
build (gcc, 3.7, 3.3)	1m 44s
build (gcc, pypy3.7, 3.3)	1m 54s
build (gcc, 3.12, 3.2)	1m 41s
build (gcc, 3.12, 3.1)	1m 34s
build (gcc, 3.12, 3.0)	1m 41s
build (gcc, 3.12, 2.7)	1m 49s
build (gcc, 3.12, 2.6)	1m 46s
build (gcc, 3.12, 2.5)	1m 44s
build (clang, 3.12, 3.3)	1m 37s
build (clang, 3.12, 3.3, test-flags-override)	1m 33s
build (clang, 3.12, 3.3, test-debug)	1m 34s
build (clang, 3.11, 3.3)	1m 42s
build (clang, 3.10, 3.3)	2m 12s
build (clang, 3.9, 3.3)	1m 46s
build (clang, 3.8, 3.3)	1m 40s
build (clang, 3.7, 3.3)	1m 44s
build (clang, pypy3.7, 3.3)	2m 8s
build (clang, 3.12, 3.2)	1m 38s
build (clang, 3.12, 3.1)	1m 49s
build (clang, 3.12, 3.0)	1m 49s
build (clang, 3.12, 2.7)	2m 4s
build (clang, 3.12, 2.6)	1m 51s
build (clang, 3.12, 2.5)	1m 52s
build (gcc, 3.12, 3.3, sanitizers)	1m 58s
	56m 55s

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