[svn-r23190] HDFFV-8285: Add suppress ddl option.

Tested: local linux

tools/testfiles/tpbitsMaxExceeded.ddl

@@ -46,6 +46,8 @@ usage: h5dump [OPTIONS] files
                           occur.
      --no-compact-subset  Disable compact form of subsetting and allow the use
                           of "[" in dataset names.
+     -O F, --ddl=F        Output ddl text into file F
+                          Use NULL as filename to suppress ddl display
 
  Subsetting is available by using the following options with a dataset
  attribute. Subsetting is done by selecting a hyperslab from the data.