licensecheck: do not look for URLs in text matches

The old code was somehow finding URLs inside text matches.
I'm not sure exactly what was wrong but I rewrote the loop header
to be simpler.

Author: rsc

testdata/Apache-2.0-Header.t1

@@ -1,7 +1,5 @@
-# BUG: Why is there a URL match inside the text match?
 100%
 Apache-2.0-Header 100.0% 0,$
-Apache-2.0 100.0% 204,242 URL
 
 Copyright [yyyy] [name of owner]
 

testdata/Apache-2.0.t1

@@ -1,7 +1,5 @@
-# BUG: URL matched in match
 100%
 Apache-2.0 100.0% 0,$
-Apache-2.0 100.0% 9904,9942 URL
 
 Apache License Version 2.0, January 2004
 http://www.apache.org/licenses/

testdata/CC-BY-4.0-URL.t1

@@ -0,0 +1,6 @@
+100%
+CC-BY-4.0 100.0% 31,$ URL
+
+This package is licensed under
+https://creativecommons.org/licenses/by/4.0/legalcode.
+

testdata/ECL-2.0.t1

@@ -1,7 +1,5 @@
-# BUG: Why did we find a URL inside the ECL-2.0 match?
 100%
 ECL-2.0 100.0% 0,$
-Apache-2.0 100.0% 365,403 URL
 
 Educational Community License Version 2.0, April 2007
 

testdata/GPL-NotLater-Header.t1

@@ -1,4 +1,3 @@
-# BUG: Should recognize
 90.6%
 GPL-NotLater-Header 100.0% 16,590
 

testdata/mixed.t1

@@ -1,6 +1,7 @@
-94.6%
-MIT 100.0% 23,1079
-BSD-3-Clause 99.5% 1188,$
+94.8%
+MIT 100% 23,1079
+BSD-3-Clause 99.5% 1188,2665
+CC-BY-4.0 100% 2704,$ URL
 
 The MIT License (MIT)
 
@@ -53,4 +54,11 @@ LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+~~~
+
+This package is licensed under
+https://creativecommons.org/licenses/by/4.0/legalcode.
+
+

testdata/mixed.t2

@@ -1,7 +1,6 @@
 # Make sure we detect CommonsClause addition.
-82.1%
+80.9%
 Apache-2.0-Header 86.7% 126,648
-Apache-2.0 100.0% 236,274 URL
 CommonsClause 100.0% 683,1397
 
 Copyright 2018 Go Gopher.