external/boringssl: Sync to e34bcc91.

This includes the following changes:

https://boringssl.googlesource.com/boringssl/+log/0e9138d295cd556e830dc8b3be735e808680f4bd..e34bcc91c07c0bf65ecc53a814d51f5246007150

This also removes BORINGSSL_ENABLE_RC4_TLS and android_compat_hacks.c as
they are no longer needed.

Test: Built tree, phone boots. Ran cts-tradefed run cts -m CtsLibcoreTestCases
Change-Id: I86df196e1856c338bbf72c60e2e47dd1b74ae537
diff --git a/src/crypto/bytestring/cbs.c b/src/crypto/bytestring/cbs.c
index c86afbd..a7adc43 100644
--- a/src/crypto/bytestring/cbs.c
+++ b/src/crypto/bytestring/cbs.c
@@ -88,13 +88,12 @@
 
 static int cbs_get_u(CBS *cbs, uint32_t *out, size_t len) {
   uint32_t result = 0;
-  size_t i;
   const uint8_t *data;
 
   if (!cbs_get(cbs, &data, len)) {
     return 0;
   }
-  for (i = 0; i < len; i++) {
+  for (size_t i = 0; i < len; i++) {
     result <<= 8;
     result |= data[i];
   }