graphs: documentation

Note that 'make web-manual' fails.

* NEWS: Document these changes.
* doc/Makefile.am: Adjust to generate example files.
* doc/bison.texi: Add a Graphviz section after "Understanding::", the section
describing the .output file, because these are similar.
* doc/figs/example-reduce.dot, doc/figs/example-reduce.txt,
doc/figs/example-shift.dot, doc/figs/example-shift.txt: New, minimal
examples to illustrate the documentation.

Signed-off-by: Akim Demaille <akim@lrde.epita.fr>

doc/figs/example-reduce.dot

@@ -0,0 +1,11 @@
+digraph "reduce.y"
+{
+  node [fontname=courier shape=box]
+  edge [fontname=courier]
+
+  1 [label="State 1\n  3 a: \"0\" .  [\".\"]\l  4 b: \"0\" .  [\";\"]\l"]
+  1 -> "1R3" [label="" style=solid]
+ "1R3" [style=filled shape=diamond fillcolor=yellowgreen label="R3"]
+  1 -> "1R4" [label="[\";\"]" style=solid]
+ "1R4" [style=filled shape=diamond fillcolor=yellowgreen label="R4"]
+}

doc/figs/example-reduce.txt

@@ -0,0 +1,15 @@
+        .------------------.
+        |     State 1      |
+        | 3 a: "0" . [";"] |
+        | 4 b: "0" . ["."] |
+        `------------------'
+              /     \
+             /       \ ["."]
+            /         \
+           v           v
+          .             .
+         / \           / \
+        / R \         / R \
+(green) \ 3 /         \ 4 / (green)
+         \ /           \ /
+          .             .

doc/figs/example-shift.dot

@@ -0,0 +1,9 @@
+digraph "shift.y"
+{
+  node [fontname=courier shape=box]
+  edge [fontname=courier]
+
+  3 [label="State 3\n  1 exp: a . \".\"\l"]
+  3 -> 6 [style=solid label="\".\""]
+  6 [label="State 6\n  1 exp: a \".\" .\l"]
+}

doc/figs/example-shift.txt

@@ -0,0 +1,12 @@
+.----------------.
+|    State 3     |
+| 1 exp: a . ";" |
+`----------------'
+        |
+        | ";"
+        |
+        v
+.----------------.
+|    State 6     |
+| 1 exp: a ";" . |
+`----------------'