Make the library usable as a library.

- Add namespace unwindstack everywhere so that it's easier for other
  code to use the library.
- Move some of the header files into include/unwindstack so that they
  can be exposed.
- Modify the headers so that only a limited number need to be exposed.
- Update the tools to use the new headers.
- Add a GetLoadBias() call on the Elf object. This prevents the need
  to get the interface object out of the Elf object.
- Move the GetRelPc() call out of the Reg class, to the Elf class. It's
  not always the case that a Reg object will be around when you want to
  get a relative pc. The tests for this moved to ElfTest.cpp.

Bug: 23762183

Test: Unit tests pass.
Change-Id: Iac609dac1dd90ed83d1a1e24ff2579c96c023bc3
diff --git a/libunwindstack/DwarfEhFrame.cpp b/libunwindstack/DwarfEhFrame.cpp
index 937b6bd..d0b35c3 100644
--- a/libunwindstack/DwarfEhFrame.cpp
+++ b/libunwindstack/DwarfEhFrame.cpp
@@ -16,12 +16,14 @@
 
 #include <stdint.h>
 
+#include <unwindstack/DwarfStructs.h>
+#include <unwindstack/Memory.h>
+
 #include "Check.h"
 #include "DwarfEhFrame.h"
-#include "DwarfMemory.h"
-#include "DwarfSection.h"
-#include "DwarfStructs.h"
-#include "Memory.h"
+#include "DwarfError.h"
+
+namespace unwindstack {
 
 template <typename AddressType>
 bool DwarfEhFrame<AddressType>::Init(uint64_t offset, uint64_t size) {
@@ -211,3 +213,5 @@
 // Explicitly instantiate DwarfEhFrame.
 template class DwarfEhFrame<uint32_t>;
 template class DwarfEhFrame<uint64_t>;
+
+}  // namespace unwindstack