cppcheck: fix warnings

- Get rid of variable that was generating false positive warning
(unitialized)

- Fix issues in tests

- Reduce scope of several variables all over

etc

Closes #2631

lib/base64.c

@@ -49,13 +49,12 @@ static size_t decodeQuantum(unsigned char *dest, const char *src)
   unsigned long i, x = 0;
 
   for(i = 0, s = src; i < 4; i++, s++) {
-    unsigned long v = 0;
-
     if(*s == '=') {
       x = (x << 6);
       padding++;
     }
     else {
+      unsigned long v = 0;
       p = base64;
 
       while(*p && (*p != *s)) {