Rename some BUF_xxx to OPENSSL_xxx

Rename BUF_{strdup,strlcat,strlcpy,memdup,strndup,strnlen}
to OPENSSL_{strdup,strlcat,strlcpy,memdup,strndup,strnlen}
Add #define's for the old names.
Add CRYPTO_{memdup,strndup}, called by OPENSSL_{memdup,strndup} macros.

Reviewed-by: Tim Hudson <tjh@openssl.org>
diff --git a/ssl/tls_srp.c b/ssl/tls_srp.c
index 64a3f23..e3763b0 100644
--- a/ssl/tls_srp.c
+++ b/ssl/tls_srp.c
@@ -179,7 +179,7 @@
         goto err;
     }
     if ((ctx->srp_ctx.login != NULL) &&
-        ((s->srp_ctx.login = BUF_strdup(ctx->srp_ctx.login)) == NULL)) {
+        ((s->srp_ctx.login = OPENSSL_strdup(ctx->srp_ctx.login)) == NULL)) {
         SSLerr(SSL_F_SSL_SRP_CTX_INIT, ERR_R_INTERNAL_ERROR);
         goto err;
     }