Windows: Include <intrin.h> when needed.

Legacy Windows did not need to #include <intrin.h> to use the MSVC
intrinsics. Newer versions likely just issue a warning, but the MSVC
documentation says to include the header file for the intrinsics we use.

GCC and Clang can "pretend" to be MSVC on Windows, so extra checks are
needed in tuklib_integer.h to only include <intrin.h> when it will is
actually needed.

src/common/tuklib_integer.h

@@ -52,6 +52,12 @@
 // and such functions.
 #if defined(__INTEL_COMPILER) && (__INTEL_COMPILER >= 1500)
 #	include <immintrin.h>
+// Only include <intrin.h> when it is needed. GCC and Clang can both
+// use __builtin's, so we only need Windows instrincs when using MSVC.
+// GCC and Clang can set _MSC_VER on Windows, so we need to exclude these
+// cases explicitly.
+#elif defined(_MSC_VER) && !TUKLIB_GNUC_REQ(3, 4) && !defined(__clang__)
+#	include <intrin.h>
 #endif
 
 

src/liblzma/common/memcmplen.h

@@ -19,6 +19,16 @@
 #	include <immintrin.h>
 #endif
 
+// Only include <intrin.h> if it is needed. The header is only needed
+// on Windows when using an MSVC compatible compiler. The Intel compiler
+// can use the intrinsics without the header file.
+#if defined(TUKLIB_FAST_UNALIGNED_ACCESS) \
+		&& (defined(_MSC_VER) \
+		&& defined(_M_X64) \
+		&& !defined(__INTEL_COMPILER))
+#	include <intrin.h>
+#endif
+
 
 /// Find out how many equal bytes the two buffers have.
 ///