Optimize RAM usage in CCM-PSK config

configs/config-ccm-psk-tls1_2.h

@@ -1,5 +1,10 @@
 /*
  * Minimal configuration for TLS 1.2 with PSK and AES-CCM ciphersuites
+ * Distinguishing features:
+ * - no bignum, no PK, no X509
+ * - fully modern and secure (provided the pre-shared keys have high entropy)
+ * - very low record overhead if using the CCM-8 suites
+ * - optimized for low RAM usage
  *
  * See README.txt for usage instructions.
  */
@@ -27,6 +32,21 @@
 #define POLARSSL_SSL_SRV_C
 #define POLARSSL_SSL_TLS_C
 
+/* Save RAM at the expense of ROM */
+#define POLARSSL_AES_ROM_TABLES
+
+/*
+ * You should adjust this to the exact number of sources you're using: default
+ * is the "platform_entrpy_poll" source, but you may want to add other ones
+ */
+#define ENTROPY_MAX_SOURCES 1
+
+/*
+ * Save RAM at the expense of interoperability: do this only if you control
+ * both ends of the connection!  (See coments in "polarssl/ssl.h".)
+ */
+#define SSL_MAX_CONTENT_LEN             512
+
 #include "check_config.h"
 
 #endif /* POLARSSL_CONFIG_H */