Revert removal of atof.c and strtod.c in r71341. We're not quite

ready for this yet---this removal should happen as part of the
py3k-short-float-repr merge.

Python/atof.c

@@ -0,0 +1,50 @@
+
+/* Just in case you haven't got an atof() around...
+   This one doesn't check for bad syntax or overflow,
+   and is slow and inaccurate.
+   But it's good enough for the occasional string literal... */
+
+#include "pyconfig.h"
+
+#include <ctype.h>
+
+double atof(char *s)
+{
+	double a = 0.0;
+	int e = 0;
+	int c;
+	while ((c = *s++) != '\0' && isdigit(c)) {
+		a = a*10.0 + (c - '0');
+	}
+	if (c == '.') {
+		while ((c = *s++) != '\0' && isdigit(c)) {
+			a = a*10.0 + (c - '0');
+			e = e-1;
+		}
+	}
+	if (c == 'e' || c == 'E') {
+		int sign = 1;
+		int i = 0;
+		c = *s++;
+		if (c == '+')
+			c = *s++;
+		else if (c == '-') {
+			c = *s++;
+			sign = -1;
+		}
+		while (isdigit(c)) {
+			i = i*10 + (c - '0');
+			c = *s++;
+		}
+		e += i*sign;
+	}
+	while (e > 0) {
+		a *= 10.0;
+		e--;
+	}
+	while (e < 0) {
+		a *= 0.1;
+		e++;
+	}
+	return a;
+}