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/tests/SymbolsTest.cpp b/libunwindstack/tests/SymbolsTest.cpp
index a0a21e6..da258a6 100644
--- a/libunwindstack/tests/SymbolsTest.cpp
+++ b/libunwindstack/tests/SymbolsTest.cpp
@@ -32,10 +32,13 @@
 #include <android-base/test_utils.h>
 #include <gtest/gtest.h>
 
-#include "Memory.h"
+#include <unwindstack/Memory.h>
+
 #include "MemoryFake.h"
 #include "Symbols.h"
 
+namespace unwindstack {
+
 template <typename TypeParam>
 class SymbolsTest : public ::testing::Test {
  protected:
@@ -333,3 +336,5 @@
 
 typedef ::testing::Types<Elf32_Sym, Elf64_Sym> SymbolsTestTypes;
 INSTANTIATE_TYPED_TEST_CASE_P(, SymbolsTest, SymbolsTestTypes);
+
+}  // namespace unwindstack