Fix URL handling in PLS parser.

Make sure relative paths are resolved to a full path.

Task-number: QTBUG-40515
Change-Id: Ideb83fc3a3c4a74c84917a22e3c30162d7b6158a
Reviewed-by: Christian Stromme <christian.stromme@digia.com>

tests/auto/unit/qmediaplaylist/testdata/test.pls

@@ -6,5 +6,22 @@ Length1=-1
 File2= http://test.host/path
 Title2=Second
 Length2=-1
+File3=testfile
+Title3=Third
+Length3=-1
 
-NumberOfEntries=2
+
+
+File4=testdir/testfile
+Title4=Fourth
+Length4=-1
+File5=/testdir/testfile
+Title5=Fifth
+Length5=-1
+File6=file://path/name#suffix
+Title6=Sixth
+Length6=-1
+File7=testfile2#suffix
+Title7=Seventh
+Length7=-1
+NumberOfEntries=7