Make test more resistant to parallelisation issues

tst/testinstall/testunix/streams.tst

@@ -3,14 +3,23 @@ gap> START_TEST("streams.tst");
 #
 # input/output streams
 #
+# GetLine can return a partial line
+gap> ReallyReadLine := function(s)
+> local out;
+> out := "";
+> while Length(out) = 0 or Last(out) <> '\n' do
+>  Append(out,ReadLine(s));
+> od;
+> return out;
+> end;;
 gap> d := DirectoryCurrent();;
 #@if ARCH_IS_UNIX()
 gap> f := Filename(DirectoriesSystemPrograms(), "cat");;
 gap> s := InputOutputLocalProcess(d,f,[]);
 < input/output stream to cat >
 gap> WriteLine(s,"The cat sat on the mat");
 true
-gap> repeat str := ReadLine(s); until str <> fail; str;
+gap> repeat str := ReallyReadLine(s); until str <> fail; str;
 "The cat sat on the mat\n"
 gap> WriteLine(s,"abc");
 true