Convert .hgignore to .gitignore.

.gitignore

@@ -0,0 +1,27 @@
+(^|/)CVS($|/)
+(^|/)\.hg($|/)
+(^|/)\.hgtags($|/)
+^plan9.log$
+^plan9-reverse.log$
+^state$
+^state.old$
+^state.journal$
+\.o$
+\.a$
+^man/man[0-9]+/.*\.html$
+^src/.*/o\.[^/]+$
+y.tab.[ch]$
+^src/cmd/rc/x.tab.h$
+^unix/.*\.tgz$
+^bin/
+^log/
+^dict/
+^postscript/font/
+\.orig$
+config
+install.log
+install.sum
+last-change
+lib/codereview/codereview.pyc
+src/cmd/awk/y.output
+src/cmd/devdraw/latin1.h