Adjust more modules to new design

Add `ecp.h` anf `timing.h` to new XXX_alt design
diff --git a/include/mbedtls/timing.h b/include/mbedtls/timing.h
index 2c497bf..bbcb906 100644
--- a/include/mbedtls/timing.h
+++ b/include/mbedtls/timing.h
@@ -30,16 +30,16 @@
 #include MBEDTLS_CONFIG_FILE
 #endif
 
-#if !defined(MBEDTLS_TIMING_ALT)
-// Regular implementation
-//
-
 #include <stdint.h>
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if !defined(MBEDTLS_TIMING_ALT)
+// Regular implementation
+//
+
 /**
  * \brief          timer structure
  */
@@ -58,6 +58,10 @@
     uint32_t                        fin_ms;
 } mbedtls_timing_delay_context;
 
+#else  /* MBEDTLS_TIMING_ALT */
+#include "timing_alt.h"
+#endif /* MBEDTLS_TIMING_ALT */
+
 extern volatile int mbedtls_timing_alarmed;
 
 /**
@@ -133,18 +137,6 @@
  */
 int mbedtls_timing_get_delay( void *data );
 
-#ifdef __cplusplus
-}
-#endif
-
-#else  /* MBEDTLS_TIMING_ALT */
-#include "timing_alt.h"
-#endif /* MBEDTLS_TIMING_ALT */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #if defined(MBEDTLS_SELF_TEST)
 /**
  * \brief          Checkup routine