Edit compatibility.md using inpage editor

Summary:
1. Modified wire compatibility.
2. IMHO it's misleading to say changing default value doesn't require code change. Some code might rely on the old default value which we don't know.

Reviewed By: thedavekwon

Differential Revision: D58245482

fbshipit-source-id: 98efd35c1bb4607ca0c33d1c5c18d1f73e4dc3c9

thrift/doc/features/compatibility.md

@@ -19,15 +19,15 @@ The following outlines the compatibility for changes to data:
 |Add a field    |yes    |yes    |Dropped by old    |
 |Remove a field    |yes    |no    |Dropped by new    |
 |Rename a field    |yes    |no    |Only affect code gen and text format    |
-|Change field type    |rarely    |no    |Only changes between utf-8 encoded string and binary are wire compatible    |
+|Change field type    |rarely    |no    |1. Changes between utf-8 encoded string and binary are wire compatible for Binary/Compact protocol. <br/>2. Changes between i32 and enum are wire compatible.    |
 |Add enum value    |yes    |yes    |Preserved by old    |
 |Remove enum value    |yes    |no    |Preserved by new    |
 |New enum field with no 0 value    |yes    |yes    |    |
 |Default on new non-optional field    |yes    |yes    |Gets new default    |
 |Default on new optional field    |yes    |yes    |Stays unset    |
-|Default changed on an non-optional field    |yes    |yes    |    |
-|Default changed on an optional field    |yes    |yes    |    |
-|Constant changed    |yes    |yes    |Old constant in old, new constant in new    |
+|Default changed on an non-optional field    |yes    |no    |    |
+|Default changed on an optional field    |yes    |no    |    |
+|Constant changed    |yes    |no    |Old constant in old, new constant in new    |
 |Required to unspecified    |yes    |no    |    |
 |Unspecified to required    |yes    |no    |    |
 |Optional to unspecified    |yes    |no    |    |