Fix fuzzer signatures.

They take a const pointer. See
http://llvm.org/docs/LibFuzzer.html#building

BUG=chromium:655016

Change-Id: Id6c7584c7a875e822b1fbff72163c888d02a9f44
Reviewed-on: https://boringssl-review.googlesource.com/11580
Reviewed-by: Steven Valdez <svaldez@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: Steven Valdez <svaldez@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
diff --git a/fuzz/read_pem.cc b/fuzz/read_pem.cc
index 511c4ee..b0c347d 100644
--- a/fuzz/read_pem.cc
+++ b/fuzz/read_pem.cc
@@ -17,7 +17,7 @@
 #include <openssl/pem.h>
 
 
-extern "C" int LLVMFuzzerTestOneInput(uint8_t *buf, size_t len) {
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *buf, size_t len) {
   char *name, *header;
   uint8_t *pem_data;
   long pem_len;