configure: port disable vfpv3 on armv6

Port 7d9d756 from io.js.

Original commit message:

  VFPv3 is ARMv7-only, enabling it for ARMv6 is therefore always wrong.
  Mea culpa, I do believe I'm the original author of that change.

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

configure

@@ -491,14 +491,14 @@ def configure_arm(o):
     arm_float_abi = 'default'
 
   if is_arch_armv7():
+    o['variables']['arm_fpu'] = 'vfpv3'
+    o['variables']['arm_neon'] = int(is_arm_neon())
     o['variables']['arm_version'] = '7'
-  elif is_arch_armv6():
-    o['variables']['arm_version'] = '6'
   else:
-    o['variables']['arm_version'] = 'default'
+    o['variables']['arm_fpu'] = 'vfpv2'
+    o['variables']['arm_neon'] = 0
+    o['variables']['arm_version'] = '6' if is_arch_armv6() else 'default'
 
-  o['variables']['arm_fpu'] = 'vfpv3'  # V8 3.18 no longer supports VFP2.
-  o['variables']['arm_neon'] = int(is_arm_neon())
   o['variables']['arm_thumb'] = 0      # -marm
   o['variables']['arm_float_abi'] = arm_float_abi