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/ElfTest.cpp b/libunwindstack/tests/ElfTest.cpp
index bf0823b..72ceb85 100644
--- a/libunwindstack/tests/ElfTest.cpp
+++ b/libunwindstack/tests/ElfTest.cpp
@@ -22,7 +22,8 @@
 
 #include <gtest/gtest.h>
 
-#include "Elf.h"
+#include <unwindstack/Elf.h>
+#include <unwindstack/MapInfo.h>
 
 #include "ElfTestUtils.h"
 #include "MemoryFake.h"
@@ -31,6 +32,8 @@
 #define PT_ARM_EXIDX 0x70000001
 #endif
 
+namespace unwindstack {
+
 class ElfTest : public ::testing::Test {
  protected:
   void SetUp() override {
@@ -237,3 +240,33 @@
   elf.InitGnuDebugdata();
   ASSERT_TRUE(elf.gnu_debugdata_interface() != nullptr);
 }
+
+class MockElf : public Elf {
+ public:
+  MockElf(Memory* memory) : Elf(memory) {}
+  virtual ~MockElf() = default;
+
+  void set_valid(bool valid) { valid_ = valid; }
+  void set_elf_interface(ElfInterface* interface) { interface_.reset(interface); }
+};
+
+TEST_F(ElfTest, rel_pc) {
+  MockElf elf(memory_);
+
+  ElfInterface* interface = new ElfInterface32(memory_);
+  elf.set_elf_interface(interface);
+
+  elf.set_valid(true);
+  interface->set_load_bias(0);
+  MapInfo map_info{.start = 0x1000, .end = 0x2000};
+
+  ASSERT_EQ(0x101U, elf.GetRelPc(0x1101, &map_info));
+
+  interface->set_load_bias(0x3000);
+  ASSERT_EQ(0x3101U, elf.GetRelPc(0x1101, &map_info));
+
+  elf.set_valid(false);
+  ASSERT_EQ(0x101U, elf.GetRelPc(0x1101, &map_info));
+}
+
+}  // namespace unwindstack