libunwindstack: add method to iterate across registers.

Add a function to iterate over Regs with a human-friendly name and the
value of the register, to make it easy to string-format registers.

Test: mma
Change-Id: I8f33830fa79b245b5030b7bc9bc3c1c7ced80c75
diff --git a/libunwindstack/Android.bp b/libunwindstack/Android.bp
index f40086e..e687a68 100644
--- a/libunwindstack/Android.bp
+++ b/libunwindstack/Android.bp
@@ -122,6 +122,7 @@
         "tests/MemoryRangeTest.cpp",
         "tests/MemoryRemoteTest.cpp",
         "tests/MemoryTest.cpp",
+        "tests/RegsIterateTest.cpp",
         "tests/RegsStepIfSignalHandlerTest.cpp",
         "tests/RegsTest.cpp",
         "tests/SymbolsTest.cpp",