Turn on -Wold-style-cast and fix the errors.

A couple of dodgy cases where we cast away const, but otherwise pretty boring.

Change-Id: Ibc39ebd525377792b5911464be842121c20f03b9
diff --git a/libc/bionic/sigdelset.cpp b/libc/bionic/sigdelset.cpp
index 3582f0d..48363d3 100644
--- a/libc/bionic/sigdelset.cpp
+++ b/libc/bionic/sigdelset.cpp
@@ -31,8 +31,8 @@
 
 int sigdelset(sigset_t* set, int signum) {
   int bit = signum - 1; // Signal numbers start at 1, but bit positions start at 0.
-  unsigned long* local_set = (unsigned long*) set;
-  if (set == NULL || bit < 0 || bit >= (int) (8*sizeof(sigset_t))) {
+  unsigned long* local_set = reinterpret_cast<unsigned long*>(set);
+  if (set == NULL || bit < 0 || bit >= static_cast<int>(8*sizeof(sigset_t))) {
     errno = EINVAL;
     return -1;
   }