build: Fixing and suppressing all warnings

clang generates a number of harmless warnings originated from cryptopp
library.

Change-Id: I676e7b6d60588867f55a2ce1cd88ef263c3e38df
diff --git a/src/security/identity/basic-identity-storage.cpp b/src/security/identity/basic-identity-storage.cpp
index 7a31c25..00df15b 100644
--- a/src/security/identity/basic-identity-storage.cpp
+++ b/src/security/identity/basic-identity-storage.cpp
@@ -207,7 +207,7 @@
       
   sqlite3_bind_text(statement, 1, identityName.toUri(), SQLITE_TRANSIENT);
   
-  int res = sqlite3_step(statement);
+  sqlite3_step(statement);
   
   sqlite3_finalize(statement);
 }
@@ -266,7 +266,7 @@
   sqlite3_bind_int(statement, 3, (int)keyType);
   sqlite3_bind_blob(statement, 4, publicKeyDer.get().buf(), publicKeyDer.get().size(), SQLITE_STATIC);
 
-  int res = sqlite3_step(statement);
+  sqlite3_step(statement);
 
   sqlite3_finalize(statement);
 }
@@ -324,7 +324,7 @@
   sqlite3_bind_text(statement, 2, identityName.toUri(), SQLITE_TRANSIENT);
   sqlite3_bind_text(statement, 3, keyId, SQLITE_TRANSIENT);
 
-  int res = sqlite3_step(statement);
+  sqlite3_step(statement);
 
   sqlite3_finalize(statement);
 }
@@ -385,7 +385,7 @@
 
   sqlite3_bind_blob(statement, 7, certificate.wireEncode().wire(), certificate.wireEncode().size(), SQLITE_STATIC);
 
-  int res = sqlite3_step(statement);
+  sqlite3_step(statement);
 
   sqlite3_finalize(statement);
 }
@@ -438,7 +438,7 @@
 
   sqlite3_bind_blob(statement, 7, certificate.wireEncode().wire(), certificate.wireEncode().size(), SQLITE_TRANSIENT);
 
-  int res = sqlite3_step(statement);
+  sqlite3_step(statement);
 
   sqlite3_finalize(statement);
 }