Move _Py_char2wchar from python.c to main.c.

This fixes issue #8441: python.c is not included
in the framework while main.c is and without this
patch you get a link error when building
Python.framework on OSX.
diff --git a/Modules/main.c b/Modules/main.c
index fa2002f..24c36db 100644
--- a/Modules/main.c
+++ b/Modules/main.c
@@ -706,6 +706,110 @@
 	*argv = orig_argv;
 }
 
+
+wchar_t*
+_Py_char2wchar(char* arg)
+{
+	wchar_t *res;
+#ifdef HAVE_BROKEN_MBSTOWCS
+	/* Some platforms have a broken implementation of
+	 * mbstowcs which does not count the characters that
+	 * would result from conversion.  Use an upper bound.
+	 */
+	size_t argsize = strlen(arg);
+#else
+	size_t argsize = mbstowcs(NULL, arg, 0);
+#endif
+	size_t count;
+	unsigned char *in;
+	wchar_t *out;
+#ifdef HAVE_MBRTOWC
+	mbstate_t mbs;
+#endif
+	if (argsize != (size_t)-1) {
+		res = (wchar_t *)PyMem_Malloc((argsize+1)*sizeof(wchar_t));
+		if (!res)
+			goto oom;
+		count = mbstowcs(res, arg, argsize+1);
+		if (count != (size_t)-1) {
+			wchar_t *tmp;
+			/* Only use the result if it contains no
+			   surrogate characters. */
+			for (tmp = res; *tmp != 0 &&
+				     (*tmp < 0xd800 || *tmp > 0xdfff); tmp++)
+				;
+			if (*tmp == 0)
+				return res;
+		}
+		PyMem_Free(res);
+	}
+	/* Conversion failed. Fall back to escaping with surrogateescape. */
+#ifdef HAVE_MBRTOWC
+	/* Try conversion with mbrtwoc (C99), and escape non-decodable bytes. */
+	
+	/* Overallocate; as multi-byte characters are in the argument, the
+	   actual output could use less memory. */
+	argsize = strlen(arg) + 1;
+	res = (wchar_t*)PyMem_Malloc(argsize*sizeof(wchar_t));
+	if (!res) goto oom;
+	in = (unsigned char*)arg;
+	out = res;
+	memset(&mbs, 0, sizeof mbs);
+	while (argsize) {
+		size_t converted = mbrtowc(out, (char*)in, argsize, &mbs);
+		if (converted == 0)
+			/* Reached end of string; null char stored. */
+			break;
+		if (converted == (size_t)-2) {
+			/* Incomplete character. This should never happen,
+			   since we provide everything that we have -
+			   unless there is a bug in the C library, or I 
+			   misunderstood how mbrtowc works. */
+			fprintf(stderr, "unexpected mbrtowc result -2\n");
+			return NULL;
+		}
+		if (converted == (size_t)-1) {
+			/* Conversion error. Escape as UTF-8b, and start over
+			   in the initial shift state. */
+			*out++ = 0xdc00 + *in++;
+			argsize--;
+			memset(&mbs, 0, sizeof mbs);
+			continue;
+		}
+		if (*out >= 0xd800 && *out <= 0xdfff) {
+			/* Surrogate character.  Escape the original
+			   byte sequence with surrogateescape. */
+			argsize -= converted;
+			while (converted--)
+				*out++ = 0xdc00 + *in++;
+			continue;
+		}
+		/* successfully converted some bytes */
+		in += converted;
+		argsize -= converted;
+		out++;
+	}
+#else
+	/* Cannot use C locale for escaping; manually escape as if charset
+	   is ASCII (i.e. escape all bytes > 128. This will still roundtrip
+	   correctly in the locale's charset, which must be an ASCII superset. */
+	res = PyMem_Malloc((strlen(arg)+1)*sizeof(wchar_t));
+	if (!res) goto oom;
+	in = (unsigned char*)arg;
+	out = res;
+	while(*in)
+		if(*in < 128)
+			*out++ = *in++;
+		else
+			*out++ = 0xdc00 + *in++;
+	*out = 0;
+#endif
+	return res;
+oom:
+	fprintf(stderr, "out of memory\n");
+	return NULL;
+}
+
 #ifdef __cplusplus
 }
 #endif