Convert VIPs to markdown format.

parsing/VIPs

@@ -1,18 +0,0 @@
-A "VIP" is a common syntax error, for which a good error message
-should be given.
-
-------------------------------------------------------------------------------
-
-Everything that is allowed in a structure but forbidden in a signature,
-or vice-versa, is a VIP. For instance, writing:
-
-  exception A = B
-
-is allowed in a structure, but forbidden in a signature. (Here, we might
-wish to make the error message depend on the lookahead token; the token
-"=" suggests that the user confuses a structure and a signature.)
-
-------------------------------------------------------------------------------
-
-Similarly, writing "struct" where "sig" is expected, or vice-versa, is
-probably a common mistake.

parsing/VIPs.md

@@ -0,0 +1,20 @@
+# VIPs
+
+A VIP is a common syntax error, for which a good error message should be
+given.
+
+## Structures versus signatures
+
+Everything that is allowed in a structure but forbidden in a signature,
+or vice-versa, is a VIP. For instance, writing:
+
+```
+  exception A = B
+```
+
+is allowed in a structure, but forbidden in a signature. (Here, we might
+wish to make the error message depend on the lookahead token; the token
+`=` suggests that the user confuses a structure and a signature.)
+
+Similarly, writing `struct` where `sig` is expected, or vice-versa, is
+probably a common mistake.