Create SECURITY.md #1220

Job	Run time
check-mingw (MINGW64, x86_64, --enable-unicode=yes)	13m 5s
check-osx	11m 55s
check-mingw (MINGW64, x86_64, --enable-static --enable-static-linking --enable-unicode=no --enabl...	11m 29s
check-ubuntu-openssl111	1m 19s
check-msvc (mscng, unicode=yes with-dl=yes)	2m 34s
check-ubuntu-openssl111 (--enable-static-linking=yes --without-nss --without-gcrypt --without-gnu...	1m 1s
check-ubuntu-openssl300	3m 30s
check-msvc (mscng, unicode=no with-dl=no static=yes legacy-crypto=yes)	2m 42s
check-ubuntu-openssl300 (--enable-static --enable-static-linking --without-nss --without-gcrypt -...	1m 20s
check-msvc (mscrypto, unicode=yes with-dl=yes)	1m 39s
check-ubuntu-openssl300 (--enable-static --enable-static-linking --enable-ftp --enable-md5 --enab...	1m 12s
check-msvc (mscrypto, unicode=no with-dl=no static=yes legacy-crypto=yes)	1m 52s
check-msvc (openssl-300, unicode=yes with-dl=yes)	6m 12s
check-msvc (openssl-300, unicode=no with-dl=no static=yes)	6m 3s
	1h 5m 53s

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