Add key management functions
Define psa_key_type_t and a first stab at a few values.
New functions psa_import_key, psa_export_key, psa_destroy_key,
psa_get_key_information. Implement them for raw data and RSA.
Under the hood, create an in-memory, fixed-size keystore with room
for MBEDTLS_PSA_KEY_SLOT_COUNT - 1 keys.
diff --git a/include/psa/crypto_platform.h b/include/psa/crypto_platform.h
index eafc0b3..7aabd1b 100644
--- a/include/psa/crypto_platform.h
+++ b/include/psa/crypto_platform.h
@@ -36,4 +36,7 @@
/* PSA requires several types which C99 provides in stdint.h. */
#include <stdint.h>
+/* Integral type representing a key slot number. */
+typedef uint16_t psa_key_slot_t;
+
#endif /* PSA_CRYPTO_PLATFORM_H */