Resubmitting 240466 after fixing the linux test suite failures.

A few extras were fixed

- Symbol::GetAddress() now returns an Address object, not a reference. There were places where people were accessing the address of a symbol when the symbol's value wasn't an address symbol. On MacOSX, undefined symbols have a value zero and some places where using the symbol's address and getting an absolute address of zero (since an Address object with no section and an m_offset whose value isn't LLDB_INVALID_ADDRESS is considered an absolute address). So fixing this required some changes to make sure people were getting what they expected. 
- Since some places want to access the address as a reference, I added a few new functions to symbol:
    Address &Symbol::GetAddressRef();
    const Address &Symbol::GetAddressRef() const;

Linux test suite passes just fine now.

<rdar://problem/21494354>

llvm-svn: 240702
diff --git a/lldb/source/Symbol/ObjectFile.cpp b/lldb/source/Symbol/ObjectFile.cpp
index b860bcf..22a313c 100644
--- a/lldb/source/Symbol/ObjectFile.cpp
+++ b/lldb/source/Symbol/ObjectFile.cpp
@@ -328,7 +328,7 @@
         {
             if (symbol->ValueIsAddress())
             {
-                const SectionSP section_sp (symbol->GetAddress().GetSection());
+                const SectionSP section_sp (symbol->GetAddressRef().GetSection());
                 if (section_sp)
                 {
                     const SectionType section_type = section_sp->GetType();