doc: output correct --help references with --program-prefix

* src/system.h (emit_ancillary_info): Take the invariant PROGRAM_NAME
as a parameter, so that consistent references are made to online docs
and texinfo nodes, when a --program-prefix is in place.  Note the
man pages don't need this fix as they're generated before the program
prefix is used.
* NEWS: Mention the improvements in references to online documentation.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/df.c b/src/df.c
index a7776652b..ccb1f5eb6 100644
--- a/src/df.c
+++ b/src/df.c
@@ -1430,7 +1430,7 @@ FIELD_LIST is a comma-separated list of columns to be included.  Valid\n\
 field names are: 'source', 'fstype', 'itotal', 'iused', 'iavail', 'ipcent',\n\
 'size', 'used', 'avail', 'pcent', 'file' and 'target' (see info page).\n\
 "), stdout);
-      emit_ancillary_info ();
+      emit_ancillary_info (PROGRAM_NAME);
     }
   exit (status);
 }