Update release notes, etc., for the 1.47.2 release #150

Job	Run time
Build and test with ASAN enabled	1m 35s
Build and test with clang	1m 14s
Cross-compile for Android (aarch64)	46s
Build and test with gcc	56s
Build and test with gcc -m32	1m 11s
Cross-compile for Android (armv7a)	35s
Build and test on macOS	1m 16s
Cross-compile for Android (i686)	28s
Cross-compile for Android (x86_64)	26s
Build mke2fs on Windows with mingw32	1m 59s
Build and test with UBSAN enabled	1m 23s
Build mke2fs on Windows with mingw64	2m 0s
	13m 49s

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