Microdumps: support aarch64 and lib mapping from APK

- Filter modules by prot flags (only +x) not extensions. It wouldn't
  otherwise catch the case of Chrome mapping the library from the
  apk (which is mapped r-x but doesn't end in .so).
- Use compile-time detection of target arch, in order to cope with
  multilib OSes, where uname() doesn't reflect the run-time arch.
- Add OS information and CPU arch / count.
- Add support for aarch64.
- Add tests and stackwalk expectations for aarch64.
- Fix a potential overflow bug in the processor.
- Rebaseline the tests using smaller symbols.
- Fix microdump_writer_unittest.cc on 32-bit host.

BUG=chromium:410294

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1407 4c0a9323-5329-0410-9bdc-e9ce6186880e

src/processor/testdata/microdump.stackwalk-arm.out

@@ -0,0 +1,42 @@
+Operating system: Android
+                  OS VERSION INFO
+CPU: armv7l
+     2 CPUs
+
+Crash reason:  
+Crash address: 0x0
+Process uptime: not available
+
+Thread 0 (crashed)
+ 0  breakpad_unittests!MicrodumpWriterTest_Setup_Test::TestBody [gtest.h : 1481 + 0x1]
+ 
+    Found by: given as instruction pointer in context
+ 1  breakpad_unittests!testing::Test::Run [gtest.cc : 2435 + 0x17]
+ 
+    Found by: call frame info
+ 2  breakpad_unittests!testing::TestInfo::Run [gtest.cc : 2610 + 0x5]
+ 
+    Found by: call frame info
+ 3  breakpad_unittests!testing::TestCase::Run [gtest.cc : 2728 + 0x3]
+ 
+    Found by: call frame info
+ 4  breakpad_unittests!testing::internal::UnitTestImpl::RunAllTests [gtest.cc : 4591 + 0x3]
+ 
+    Found by: call frame info
+ 5  breakpad_unittests!testing::UnitTest::Run [gtest.cc : 2418 + 0x5]
+ 
+    Found by: call frame info
+ 6  breakpad_unittests!main [gtest.h : 2326 + 0x3]
+ 
+    Found by: call frame info
+ 7  libc.so + 0x11e9d
+ 
+    Found by: call frame info
+
+Loaded modules:
+0xaaacd000 - 0xaab48fff  breakpad_unittests  ???
+0xf6fca000 - 0xf6fcdfff  libnetd_client.so  ???
+0xf6fee000 - 0xf6ff1fff  libstdc++.so  ???
+0xf6ff2000 - 0xf700afff  libm.so  ???
+0xf700c000 - 0xf7012fff  liblog.so  ???
+0xf7014000 - 0xf706dfff  libc.so  ???  (WARNING: No symbols, libc.so, 167F187B09A27F7444EF989603AAFD3D0)