Add .gitignore everywhere based on .cvsignore.

* .gitignore: New.
* build-aux/.gitignore: New.
* data/.gitignore: New.
* doc/.gitignore: New.
* etc/.gitignore: New.
* examples/.gitignore: New.
* examples/calc++/.gitignore: New.
* lib/.gitignore: New.
* m4/.gitignore: New.
* po/.gitignore: New.
* runtime-po/.gitignore: New.
* src/.gitignore: New.
* tests/.gitignore: New.

doc/.gitignore

@@ -0,0 +1,24 @@
+/Makefile
+/bison.aux
+/bison.cp
+/bison.cps
+/bison.dvi
+/bison.fn
+/bison.html
+/bison.ky
+/bison.log
+/bison.pdf
+/bison.pg
+/bison.ps
+/bison.toc
+/bison.tp
+/bison.vr
+/cross-options.texi
+/Makefile.in
+/refcard.dvi
+/refcard.log
+/refcard.ps
+/*.info*
+/stamp-vti
+/version.texi
+/yacc.1