add external dependencies in a pre-built way to avoid incompatibilities

external/include/sodium/crypto_core_salsa208.h

@@ -0,0 +1,40 @@
+#ifndef crypto_core_salsa208_H
+#define crypto_core_salsa208_H
+
+#include <stddef.h>
+#include "export.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define crypto_core_salsa208_OUTPUTBYTES 64U
+SODIUM_EXPORT
+size_t crypto_core_salsa208_outputbytes(void)
+            __attribute__ ((deprecated));
+
+#define crypto_core_salsa208_INPUTBYTES 16U
+SODIUM_EXPORT
+size_t crypto_core_salsa208_inputbytes(void)
+            __attribute__ ((deprecated));
+
+#define crypto_core_salsa208_KEYBYTES 32U
+SODIUM_EXPORT
+size_t crypto_core_salsa208_keybytes(void)
+            __attribute__ ((deprecated));
+
+#define crypto_core_salsa208_CONSTBYTES 16U
+SODIUM_EXPORT
+size_t crypto_core_salsa208_constbytes(void)
+            __attribute__ ((deprecated));
+
+SODIUM_EXPORT
+int crypto_core_salsa208(unsigned char *out, const unsigned char *in,
+                         const unsigned char *k, const unsigned char *c)
+            __attribute__ ((nonnull(1, 2, 3)));
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif