Update UPGRADING wrt. [RFC]: Add Argon2 to password_*

Author: cmb69

UPGRADING

@@ -32,6 +32,10 @@ PHP 7.2 UPGRADE NOTES
 - PCRE:
   . Added `J` modifier for setting PCRE_DUPNAMES.
 
+- Standard:
+  . Simplified password hashing API updated to support Argon2i hashes when PHP is compiled with libargon2
+    (https://wiki.php.net/rfc/argon2_password_hash).
+
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 3. Changes in SAPI modules
 ========================================
@@ -44,6 +48,14 @@ PHP 7.2 UPGRADE NOTES
 5. Changed Functions
 ========================================
 
+- Standard:
+  . password_hash() can generate Argon2i hashes when the algorithm is set to PASSWORD_ARGON2I. 
+    When using PASSWORD_ARGON2I, the following cost factors may be set: 'memory_cost', 'time_cost', 
+    and 'threads'. These cost factors will default to 'PASSWORD_ARGON2_DEFAULT_MEMORY_COST', 
+    'PASSWORD_ARGON2_DEFAULT_TIME_COST', and 'PASSWORD_ARGON2_DEFAULT_THREADS' respectively if not set.
+  . password_verify() can verify Argon2i hashes.
+  . password_get_info() and password_needs_rehash() can accept Argon2i hashes.
+
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 6. New Functions
 ========================================
@@ -82,6 +94,12 @@ PHP 7.2 UPGRADE NOTES
 10. New Global Constants
 ========================================
 
+- Standard:
+  . PASSWORD_ARGON2_DEFAULT_MEMORY_COST
+  . PASSWORD_ARGON2_DEFAULT_TIME_COST
+  . PASSWORD_ARGON2_DEFAULT_THREADS
+  . PASSWORD_ARGON2I
+
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 11. Changes to INI File Handling
 ========================================