Debug info: Properly handle the function prologue in the line table.

Introduces a new flag in SILLocation: InPrologue to mark instructions
that setup the stack and allocate storage for local variables/arguments.

Fixes rdar://problem/15290023: Breakpoint set on prologue - crash ensues.

Swift SVN r9686

lib/SIL/SILPrinter.cpp

@@ -406,7 +406,7 @@ public:
           case SILLocation::InlinedKind :
             OS << ":inlined"; break;
           case SILLocation::MandatoryInlinedKind :
-              OS << ":minlined"; break;
+            OS << ":minlined"; break;
           case SILLocation::CleanupKind :
             OS << ":cleanup"; break;
           case SILLocation::ArtificialUnreachableKind :
@@ -416,7 +416,8 @@ public:
           }
           if (L.isAutoGenerated())
             OS << ":auto_gen";
-
+          if (L.isInPrologue())
+            OS << ":in_prologue";
         }
         if (L.isNull()) {
           if (!printedSlashes) {