add a credits file for libc++

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@119390 91177308-0d34-0410-b5e6-96231b3b80d8

CREDITS.TXT

@@ -0,0 +1,15 @@
+This file is a partial list of people who have contributed to the LLVM/libc++
+project.  If you have contributed a patch or made some other contribution to
+LLVM/libc++, please submit a patch to this file to add yourself, and it will be
+done!
+
+The list is sorted by surname and formatted to allow easy grepping and
+beautification by scripts.  The fields are: name (N), email (E), web-address
+(W), PGP key ID and fingerprint (P), description (D), and snail-mail address
+(S).
+
+N: Howard Hinnant
+E: hhinnant@apple.com
+D: Architect and primary author of libc++
+
+