Revert "Remove V8_HOST_CAN_READ_UNALIGNED and its uses."

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 2bf57c96338092fb06550e4d4fcf79a11ea19982..22b944be9705fc8dc29c0992981ec12e2bf8b61e 100644
--- a/src/base/build_config.h
+++ b/src/base/build_config.h
@@ -21,6 +21,7 @@
 // V8_HOST_ARCH_IA32 on both 32- and 64-bit x86.
 #define V8_HOST_ARCH_IA32 1
 #define V8_HOST_ARCH_32_BIT 1
+#define V8_HOST_CAN_READ_UNALIGNED 1
 #else
 #define V8_HOST_ARCH_X64 1
 #if defined(__x86_64__) && __SIZEOF_POINTER__ == 4  // Check for x32.
@@ -28,13 +29,16 @@
 #else
 #define V8_HOST_ARCH_64_BIT 1
 #endif
+#define V8_HOST_CAN_READ_UNALIGNED 1
 #endif  // __native_client__
 #elif defined(_M_IX86) || defined(__i386__)
 #define V8_HOST_ARCH_IA32 1
 #define V8_HOST_ARCH_32_BIT 1
+#define V8_HOST_CAN_READ_UNALIGNED 1
 #elif defined(__AARCH64EL__)
 #define V8_HOST_ARCH_ARM64 1
 #define V8_HOST_ARCH_64_BIT 1
+#define V8_HOST_CAN_READ_UNALIGNED 1
 #elif defined(__ARMEL__)
 #define V8_HOST_ARCH_ARM 1
 #define V8_HOST_ARCH_32_BIT 1