Update BearSSL, increase SSL stack (#6980)

Only minor updates to headers and no functionality change on the
portions that we use in the ESP8266.

@Teddyz reported random crashes while running against a local MQTT
server and was able to report stack usages of up to 6136 bytes.
Increase the SSL stack to a little more than that, once again.

Author: earlephilhower

Diff for: cores/esp8266/StackThunk.cpp

@@ -36,8 +36,8 @@ uint32_t *stack_thunk_top = NULL;
 uint32_t *stack_thunk_save = NULL;  /* Saved A1 while in BearSSL */
 uint32_t stack_thunk_refcnt = 0;
 
-/* Largest stack usage seen in the wild at scripts.google.com at 5828 */
-#define _stackSize (5900/4)
+/* Largest stack usage seen in the wild at  6120 */
+#define _stackSize (6200/4)
 #define _stackPaint 0xdeadbeef
 
 /* Add a reference, and allocate the stack if necessary */

Diff for: tools/sdk/include/bearssl/bearssl_ec.h

@@ -108,7 +108,7 @@ extern "C" {
  *
  *   - The multipliers (integers) MUST be lower than the subgroup order.
  *     If this property is not met, then the result is indeterminate,
- *     but an error value is not ncessearily returned.
+ *     but an error value is not necessarily returned.
  * 
  *
  * ## ECDSA

Diff for: tools/sdk/include/bearssl/bearssl_git.h

@@ -1,2 +1,2 @@
 // Do not edit -- Automatically generated by tools/sdk/ssl/bearssl/Makefile
-#define BEARSSL_GIT 89454af
+#define BEARSSL_GIT 0645c68

Diff for: tools/sdk/include/bearssl/bearssl_ssl.h

@@ -2114,7 +2114,7 @@ void br_ssl_engine_sendapp_ack(br_ssl_engine_context *cc, size_t len);
 /**
  * \brief Get buffer for received application data.
  *
- * If the engine has received application data from the peer, hen this
+ * If the engine has received application data from the peer, then this
  * call returns a pointer to the buffer from where such data shall be
  * read, and its length is written in `*len`. Otherwise, `*len` is set
  * to 0 and `NULL` is returned.