Avoid copying unaligned 16-bit values since some platforms require them to be...

Avoid copying unaligned 16-bit values since some platforms require them to be aligned. Use memcpy() instead to let the C compiler decide how to do it.

Closes https://github.com/cython/cython/issues/4343

Cython/Utility/TypeConversion.c

@@ -702,22 +702,11 @@ static const char DIGITS_HEX[2*16+1] = {
 static CYTHON_INLINE PyObject* {{TO_PY_FUNCTION}}({{TYPE}} value, Py_ssize_t width, char padding_char, char format_char);
 
 /////////////// CIntToPyUnicode ///////////////
+//@requires: StringTools.c::IncludeStringH
 //@requires: StringTools.c::BuildPyUnicode
 //@requires: CIntToDigits
 //@requires: GCCDiagnostics
 
-#ifdef _MSC_VER
-    #ifndef _MSC_STDINT_H_
-        #if _MSC_VER < 1300
-           typedef unsigned short    uint16_t;
-        #else
-           typedef unsigned __int16  uint16_t;
-        #endif
-    #endif
-#else
-   #include <stdint.h>
-#endif
-
 // NOTE: inlining because most arguments are constant, which collapses lots of code below
 
 static CYTHON_INLINE PyObject* {{TO_PY_FUNCTION}}({{TYPE}} value, Py_ssize_t width, char padding_char, char format_char) {
@@ -755,14 +744,14 @@ static CYTHON_INLINE PyObject* {{TO_PY_FUNCTION}}({{TYPE}} value, Py_ssize_t wid
             digit_pos = abs((int)(remaining % (8*8)));
             remaining = ({{TYPE}}) (remaining / (8*8));
             dpos -= 2;
-            *(uint16_t*)dpos = ((const uint16_t*)DIGIT_PAIRS_8)[digit_pos]; /* copy 2 digits at a time */
+            memcpy(dpos, DIGIT_PAIRS_8 + digit_pos * 2, 2); /* copy 2 digits at a time, unaligned */
             last_one_off = (digit_pos < 8);
             break;
         case 'd':
             digit_pos = abs((int)(remaining % (10*10)));
             remaining = ({{TYPE}}) (remaining / (10*10));
             dpos -= 2;
-            *(uint16_t*)dpos = ((const uint16_t*)DIGIT_PAIRS_10)[digit_pos]; /* copy 2 digits at a time */
+            memcpy(dpos, DIGIT_PAIRS_10 + digit_pos * 2, 2); /* copy 2 digits at a time, unaligned */
             last_one_off = (digit_pos < 10);
             break;
         case 'x':