Fix typos throughout the license files that somehow I and my reviewers

all missed!

Thanks to Alex Bradbury for pointing this out, and the fact that I never
added the intended `legacy` anchor to the developer policy. Add that
anchor too. With hope, this will cause the links to all resolve
successfully.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@351731 91177308-0d34-0410-b5e6-96231b3b80d8

LICENSE.TXT

@@ -234,7 +234,7 @@ mechanisms:
    file.
 
 ==============================================================================
-Legacy LLVM License (ttps://llvm.org/docs/DeveloperPolicy.html#legacy):
+Legacy LLVM License (https://llvm.org/docs/DeveloperPolicy.html#legacy):
 ==============================================================================
 
 The libc++ library is dual licensed under both the University of Illinois