ARM: add AArch32 support and new vcvt instructions

src/base/build_config.h

Index: src/base/build_config.h
diff --git a/src/base/build_config.h b/src/base/build_config.h
index e412b92dfef4f4c919ddc87dc8303a00aa41a277..8724bfb111303be7bcf590f2b01c54763267dd52 100644
--- a/src/base/build_config.h
+++ b/src/base/build_config.h
@@ -55,6 +55,25 @@
 #endif
 
 
+#if defined(__ARM_ARCH_8A__) || \
+    defined(__ARM_ARCH_8R__) || \
+    defined(__ARM_ARCH_8__)
+# define CAN_USE_ARMV8_INSTRUCTIONS 1
+# ifndef CAN_USE_ARMV7_INSTRUCTIONS
+#  define CAN_USE_ARMV7_INSTRUCTIONS 1
+# endif
+# ifndef CAN_USE_VFP3_INSTRUCTIONS
+#  define CAN_USE_VFP3_INSTRUCTIONS
+# endif
+# ifndef CAN_USE_VFP32DREGS
+#  define CAN_USE_VFP32DREGS
+# endif
+# ifndef CAN_USE_NEON
+#  define CAN_USE_NEON
+#endif
+#endif
+
+
 // Target architecture detection. This may be set externally. If not, detect
 // in the same way as the host architecture, that is, target the native
 // environment as presented by the compiler.