global: remove unnecessary horizontal tabs.

This change was made by applying emacs' untabify function to
nearly all files in Bison's repository.  Required tabs in make
files, ChangeLog, regexps, and test code were manually skipped.
Other notable exceptions and changes are listed below.
* bootstrap: Skip because we sync this with gnulib.
* data/m4sugar/foreach.m4
* data/m4sugar/m4sugar.m4: Skip because we sync these with
Autoconf.
* djgpp: Skip because I don't know how to test djgpp properly, and
this code appears to be unmaintained anyway.
* README-hacking (Hacking): Specify that tabs should be avoided
where not required.

src/graphviz.h

@@ -40,7 +40,7 @@ void output_node (int id, char const *label, FILE *fout);
 /// \param style        Dot style of the edge (e.g., "dotted" or "solid").
 /// \param fout         output stream.
 void output_edge (int source, int destination, char const *label,
-		  char const *style, FILE *fout);
+                  char const *style, FILE *fout);
 
 /// End a Dot graph.
 /// \param fout  output stream.