Add missing newlines at EOF in sources

(missing newlines break build due to -Werror)

Author: AMDmi3

core/friend_requests.h

@@ -48,4 +48,4 @@ int friendreq_handlepacket(uint8_t *packet, uint32_t length, IP_Port source);
 }
 #endif
 
-#endif
+#endif

testing/Lossless_UDP_testclient.c

@@ -211,4 +211,4 @@ int main(int argc, char *argv[])
     }
 
     return 0;
-}
+}

testing/Lossless_UDP_testserver.c

@@ -198,4 +198,4 @@ int main(int argc, char *argv[])
     }
 
     return 0;
-}
+}

testing/misc_tools.h

@@ -26,4 +26,4 @@
 
 unsigned char * hex_string_to_bin(char hex_string[]);
 
-#endif // MISC_TOOLS_H
+#endif // MISC_TOOLS_H