Fix printing of strings inside functions

Previously we normalised all whitespace in printed out functions,
which would effect whitespace inside strings.

lib/function.gi

@@ -78,13 +78,13 @@ end);
 
 InstallMethod(String, "for a function, with whitespace reduced", [IsFunction and IsInternalRep],
 function(fun)
-    local  s, stream;
+    local  s, stream,lines, pos, i;
     s := "";
     stream := OutputTextString(s, true);
+    SetPrintFormattingStatus(stream, false);
     PrintTo(stream, fun);
     CloseStream(stream);
-    NormalizeWhitespace(s);
-    return MakeImmutable(s);
+    return ReplacedString(s, "\n", " ");
 end);
 
 BIND_GLOBAL( "VIEW_STRING_OPERATION",

tst/testinstall/function.tst

@@ -137,6 +137,31 @@ gap> Print({x,y} -> x + y, "\n");
 function ( x, y )
     return x + y;
 end
+gap> String({x,y} -> x + y);
+"function ( x, y ) return x + y; end"
+
+# Test nesting
+gap> Print(function(x) if x then if x then while x do od; fi; fi; end, "\n");
+function ( x )
+    if x then
+        if x then
+            while x do
+                ;
+            od;
+        fi;
+    fi;
+    return;
+end
+gap> String(function(x) if x then if x then while x do od; fi; fi; end);
+"function ( x ) if x then if x then while x do ; od; fi; fi; return; end"
+
+# Check strings in functions
+gap> Print({x} -> "a     b","\n");
+function ( x )
+    return "a     b";
+end
+gap> String({x} -> "a     b");
+"function ( x ) return \"a     b\"; end"
 gap> f := ({x,y} -> x + y);
 function( x, y ) ... end
 gap> f(2,3);