Unify coding style

@sjaeckel integrated clang-format with formal coding style. Run his
script and commit changes.

There are pros and cons of this commit.

Mixed coding style is a "broken window". A good single style simplifies
reading and writing code.

On the other hand, this is a big change which will lead to conflicts.

src/tls_dummy.c

@@ -70,12 +70,12 @@ int tls_pending(tls_t *tls)
     return 0;
 }
 
-int tls_read(tls_t *tls, void * const buff, const size_t len)
+int tls_read(tls_t *tls, void *const buff, const size_t len)
 {
     return -1;
 }
 
-int tls_write(tls_t *tls, const void * const buff, const size_t len)
+int tls_write(tls_t *tls, const void *const buff, const size_t len)
 {
     return -1;
 }