special case: recognize '[^\n]' and make it as fast as '.'

R=rsc
DELTA=25  (23 added, 1 deleted, 1 changed)
OCL=32793
CL=32799
diff --git a/src/pkg/regexp/all_test.go b/src/pkg/regexp/all_test.go
index 23c2200..0d16b24 100644
--- a/src/pkg/regexp/all_test.go
+++ b/src/pkg/regexp/all_test.go
@@ -27,6 +27,7 @@
 	`[]`,
 	`[abc]`,
 	`[^1234]`,
+	`[^\n]`,
 }
 
 // TODO: nice to do this with a map
@@ -72,6 +73,7 @@
 	tester{ `[a-z]+`,	"abcd",	vec{0,4} },
 	tester{ `[^a-z]+`,	"ab1234cd",	vec{2,6} },
 	tester{ `[a\-\]z]+`,	"az]-bcz",	vec{0,4} },
+	tester{ `[^\n]+`,	"abcd\n",	vec{0,4} },
 	tester{ `[日本語]+`,	"日本語日本語",	vec{0,18} },
 	tester{ `()`,	"",	vec{0,0, 0,0} },
 	tester{ `(a)`,	"a",	vec{0,1, 0,1} },