Move README to dist subdirectory

README was originally written for users of distribution tarballs.
Nowadays it appears to be confusing for those who build strace
using a GIT version of strace source code.

* README: Move...
* dist/README: ...here.
* bootstrap: Copy README from dist subdirectory to the toplevel
directory after successful autoreconf.

Co-Authored-by: Dmitry V. Levin <ldv@altlinux.org>
References: https://github.com/strace/strace/issues/56

.gitignore

@@ -51,6 +51,7 @@
 /native_printer_decls.h
 /native_printer_defs.h
 /printers.h
+/README
 /scno.h
 /sen.h
 /stamp-h1

bootstrap

@@ -25,4 +25,8 @@ for m in m32 mx32; do
 	done
 done
 
-exec autoreconf -f -i "$@"
+autoreconf -f -i "$@"
+
+for f in README; do
+	cp "dist/$f" "$f"
+done