implement a64l and l64a (legacy xsi stuff)

src/misc/a64l.c

+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+
+static const char digits[] =
+	"./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
+
+long a64l(const char *s)
+{
+	int e;
+	uint32_t x = 0;
+	for (e=0; e<36 && *s; e+=6, s++)
+		x |= (strchr(digits, *s)-digits)<<e;
+	return x;
+}
+
+char *l64a(long x0)
+{
+	static char s[7];
+	char *p;
+	uint32_t x = x0;
+	for (p=s; x; p++, x>>=6)
+		*p = digits[x&63];
+	*p = 0;
+	return s;
+}