[Reflection] Fix several issues for COFF and ELF

Previously when ReflectionContext was parsing the image of a binary
(for ELF or COFF) it was making some incorrect assumptions about the location
of sections in the memory of a remote process. In particular, it was using the offsets
rather than the virtual addresses and it was incorrectly calculating the references (relative pointers)
inside the metadata. In this diff we address these issues and adjust swift-reflection-dump
(used in tests) to emulate the runtime behavior more closely.
This diff has been extensively tested, the reflection tests are green on OSX and Linux,
on Windows it fixes 2 new tests:
    Reflection/typeref_decoding.swift
    stdlib/ReflectionHashing.swift
So now (with some minor fixes to the lit testsing infrastructure) the following reflection
tests pass:
    Reflection/box_descriptors.sil
    Reflection/capture_descriptors.sil
    Reflection/typeref_decoding.swift
    stdlib/ReflectionHashing.swift

Author: Alexander Shaposhnikov

include/swift/Reflection/ReflectionContext.h

@@ -322,14 +322,21 @@ class ReflectionContext
                 : llvm::StringRef(COFFSec->Name, llvm::COFF::NameSize);
         if (SectionName != Name)
           continue;
-        auto Addr = ImageStart.getAddressData() + COFFSec->PointerToRawData;
+        auto Addr = ImageStart.getAddressData() + COFFSec->VirtualAddress;
         auto Buf = this->getReader().readBytes(RemoteAddress(Addr),
                                                COFFSec->VirtualSize);
         const char *Begin = reinterpret_cast<const char *>(Buf.get());
         const char *End = Begin + COFFSec->VirtualSize;
         savedBuffers.push_back(std::move(Buf));
-        return {{Begin, End},
-                COFFSec->VirtualAddress - COFFSec->PointerToRawData};
+
+        // FIXME: This code needs to be cleaned up and updated
+        // to make it work for 32 bit platforms.
+        if (SectionName != ".sw5cptr") {
+          Begin += 8;
+          End -= 8;
+        }
+
+        return {{Begin, End}, 0};
       }
       return {{nullptr, nullptr}, 0};
     };
@@ -338,20 +345,15 @@ class ReflectionContext
         findCOFFSectionByName(".sw5cptr");
     std::pair<std::pair<const char *, const char *>, uint32_t> TypeRefMdSec =
         findCOFFSectionByName(".sw5tyrf");
-
-    // FIXME: Make use of .sw5flmd section (the section content appears to be
-    // incorrect on Windows at the moment).
-    std::pair<std::pair<const char *, const char *>, uint32_t> FieldMdSec = {
-        {nullptr, nullptr}, 0};
-    // FIXME: Make use of .sw5asty.
-    std::pair<std::pair<const char *, const char *>, uint32_t> AssocTySec = {
-        {nullptr, nullptr}, 0};
-    // FIXME: Make use of .sw5bltn.
-    std::pair<std::pair<const char *, const char *>, uint32_t> BuiltinTySec = {
-        {nullptr, nullptr}, 0};
-    // FIXME: Make use of .sw5repl.
-    std::pair<std::pair<const char *, const char *>, uint32_t> ReflStrMdSec = {
-        {nullptr, nullptr}, 0};
+    std::pair<std::pair<const char *, const char *>, uint32_t> FieldMdSec =
+        findCOFFSectionByName(".sw5flmd");
+    std::pair<std::pair<const char *, const char *>, uint32_t> AssocTySec =
+        findCOFFSectionByName(".sw5asty");
+    // FIXME: Use the section .sw5bltn instead.
+    std::pair<std::pair<const char *, const char *>, uint32_t> BuiltinTySec =
+        {{nullptr, nullptr}, 0};
+    std::pair<std::pair<const char *, const char *>, uint32_t> ReflStrMdSec =
+        findCOFFSectionByName(".sw5rfst");
 
     if (FieldMdSec.first.first == nullptr &&
         AssocTySec.first.first == nullptr &&
@@ -457,12 +459,11 @@ class ReflectionContext
         if (SecName != Name)
           continue;
         auto SecStart =
-            RemoteAddress(ImageStart.getAddressData() + Hdr->sh_offset);
+            RemoteAddress(ImageStart.getAddressData() + Hdr->sh_addr);
         auto SecSize = Hdr->sh_size;
         auto SecBuf = this->getReader().readBytes(SecStart, SecSize);
         auto SecContents = reinterpret_cast<const char *>(SecBuf.get());
-        return {{SecContents, SecContents + SecSize},
-                Hdr->sh_addr - Hdr->sh_offset};
+        return {{SecContents, SecContents + SecSize}, 0};
       }
       return {{nullptr, nullptr}, 0};
     };