deps: port fix v8 armv6 run-time detection

Port 297cadb from io.js.

Original commit message:

  The elf_platform suffix in /proc/cpuinfo moved to the model name field
  in Linux 3.8.

  Out-of-tree patch pending https://codereview.chromium.org/867713003/

  Fixes: nodejs/node#283
  PR-URL: nodejs/node#559
  Reviewed-By: Fedor Indutny <fedor@indutny.com>

deps/v8/src/base/cpu.cc

@@ -365,7 +365,7 @@ CPU::CPU() : stepping_(0),
     //
     // See http://code.google.com/p/android/issues/detail?id=10812
     //
-    // We try to correct this by looking at the 'elf_format'
+    // We try to correct this by looking at the 'elf_platform'
     // field reported by the 'Processor' field, which is of the
     // form of "(v7l)" for an ARMv7-based CPU, and "(v6l)" for
     // an ARMv6-one. For example, the Raspberry Pi is one popular
@@ -377,6 +377,15 @@ CPU::CPU() : stepping_(0),
       }
       delete[] processor;
     }
+
+    // elf_platform moved to the model name field in Linux v3.8.
+    if (architecture_ == 7) {
+      char* processor = cpu_info.ExtractField("model name");
+      if (HasListItem(processor, "(v6l)")) {
+        architecture_ = 6;
+      }
+      delete[] processor;
+    }
   }
 
   // Try to extract the list of CPU features from ELF hwcaps.