Add libunwindstack support for Mips and Mips64

This patch requires v3.18 kernel or above, because v3.10 kernel
has a bug (as of 8/1/2017) in the ptrace(GETREGSET) function for mips
and mips64.

Change-Id: I004c1fa190193eebe1c84440b366289122a6bd8a
Signed-off-by: Douglas Leung <douglas.leung@mips.com>
Signed-off-by: Dejan Jovicevic <dejan.jovicevic@mips.com>
diff --git a/libunwindstack/tools/unwind.cpp b/libunwindstack/tools/unwind.cpp
index 7896279..81bedb7 100644
--- a/libunwindstack/tools/unwind.cpp
+++ b/libunwindstack/tools/unwind.cpp
@@ -76,6 +76,12 @@
     case unwindstack::ARCH_X86_64:
       printf("x86_64");
       break;
+    case unwindstack::ARCH_MIPS:
+      printf("mips");
+      break;
+    case unwindstack::ARCH_MIPS64:
+      printf("mips64");
+      break;
     default:
       printf("unknown\n");
       return;