Add MSYS2_PKG_UPDATE rule and use in msys2 packages * Makefile.in: add MSYS2_PKG_UPDATE def * src/msys2-bash.mk, src/msys2-coreutils.mk, src/msys2-diffutils.mk, src/msys2-dos2unix.mk, src/msys2-filesystem.mk, src/msys2-findutils.mk, src/msys2-gawk.mk, src/msys2-gcc-libs.mk, src/msys2-gmp.mk, src/msys2-gnupg.mk, src/msys2-grep.mk, src/msys2-gzip.mk, src/msys2-icu.mk, src/msys2-info.mk, src/msys2-keyring.mk, src/msys2-less.mk, src/msys2-libassuan.mk, src/msys2-libbz2.mk, src/msys2-libcrypt.mk, src/msys2-libexpat.mk, src/msys2-libffi.mk, src/msys2-libgcrypt.mk, src/msys2-libgnutls.mk, src/msys2-libgpg-error.mk, src/msys2-libgpgme.mk, src/msys2-libhogweed.mk, src/msys2-libiconv.mk, src/msys2-libidn2.mk, src/msys2-libintl.mk, src/msys2-libksba.mk, src/msys2-liblzma.mk, src/msys2-libmetalink.mk, src/msys2-libnettle.mk, src/msys2-libnpth.mk, src/msys2-libopenssl.mk, src/msys2-libp11-kit.mk, src/msys2-libpcre.mk, src/msys2-libpsl.mk, src/msys2-libreadline.mk, src/msys2-libsqlite.mk, src/msys2-libtasn1.mk, src/msys2-libunistring.mk, src/msys2-libutil-linux.mk, src/msys2-libxml2.mk, src/msys2-make.mk, src/msys2-mintty.mk, src/msys2-mpfr.mk, src/msys2-ncurses.mk, src/msys2-pacman-mirrors.mk, src/msys2-pacman.mk, src/msys2-patch.mk, src/msys2-perl.mk, src/msys2-runtime.mk, src/msys2-sed.mk, src/msys2-tar.mk, src/msys2-unzip.mk, src/msys2-wget.mk, src/msys2-zip.mk, src/msys2-zlib.mk: use MSYS2_PKG_UPDATE