Add comment to explain change of OPAQUE to OPAQUE_
@@ -175,7 +175,7 @@ NCConstant constant;
TYPES
COMPOUND
ENUM
- OPAQUE_
+ OPAQUE_ /* 'OPAQUE' apparently conflicts with HDF4 code */
OPAQUESTRING /* 0x<even number of hexdigits> */
GROUP
PATH /* / or (/IDENT)+(.IDENT)? */
