Make deserialized locations default to line 0, which tells the debugger

to ignore them, while still referencing the module file needed to perform
type lookups, etc.
<rdar://problem/17648201> After setting a breakpoint, the first step action is malfunctioning

Swift SVN r20801

Author: adrian-prantl

lib/IRGen/IRGenDebugInfo.cpp

@@ -231,7 +231,7 @@ Location getDeserializedLoc(Decl* D)  {
   const DeclContext *DC = D->getDeclContext()->getModuleScopeContext();
   if (const char *Filename = getFilenameFromDC(DC)) {
     L.Filename = Filename;
-    L.Line = 1;
+    L.Line = 0;
   }
   return L;
 }

test/DebugInfo/Imports.swift

@@ -7,7 +7,7 @@
 // CHECK-DAG: ![[THISFILE]] = metadata {{.*}}[ DW_TAG_file_type ] [{{.*}}test/DebugInfo/Imports.swift]
 // CHECK-DAG: ![[SWIFTFILE:[0-9]+]] = {{.*}}[ DW_TAG_file_type ]{{.*}}Swift.swiftmodule
 // CHECK-DAG: ![[SWIFTMODULE:[0-9]+]] = {{.*}}[ DW_TAG_module ] [Swift]
-// CHECK-DAG: metadata ![[SWIFTFILE]], metadata ![[SWIFTMODULE]], i32 1} ; [ DW_TAG_imported_module ]
+// CHECK-DAG: metadata ![[SWIFTFILE]], metadata ![[SWIFTMODULE]], i32 0} ; [ DW_TAG_imported_module ]
 // CHECK-DAG: metadata ![[BASICFILE:[0-9]+]], metadata ![[BASICMODULE:[0-9]+]], i32 [[@LINE+3]]} ; [ DW_TAG_imported_module ]
 // CHECK-DAG: ![[BASICFILE]] = {{.*}}basic.swift
 // CHECK-DAG: ![[BASICMODULE]] = {{.*}}[ DW_TAG_module ] [basic]

test/DebugInfo/basic.swift

@@ -63,7 +63,7 @@ func foo(var a: Int, var b: Int) -> Int {
 
 // Import of the swift standard library.
 // CHECK-DAG: ![[SWIFTFILE:[0-9]+]] = {{.*}}DW_TAG_file_type{{.*}}Swift.swiftmodule
-// CHECK-DAG: metadata ![[SWIFTFILE]], metadata ![[SWIFTMODULE:[0-9]+]], i32 1} ; [ DW_TAG_imported_module ]
+// CHECK-DAG: metadata ![[SWIFTFILE]], metadata ![[SWIFTMODULE:[0-9]+]], i32 0} ; [ DW_TAG_imported_module ]
 // CHECK-DAG: ![[SWIFTMODULE]] = {{.*}}[ DW_TAG_module ] [Swift]
 
 // Filenames