/ is no longer a reserved char for urlEncode()

This change is a quick hack solving known issues with URI-encoding in
libkiwix.

This change removes the slash character from the list of URL separator
symbols in URL encoding/decoding utilities, and makes it a symbol that
is safe to leave unencoded.

Effects:

- `urlEncode()` never encodes the '/' symbol (even when it is requested
  to encode the URL separator symbols too).

- `urlDecode(str)`/`urlDecode(..., false)` will now decode %2F to '/';
  other encoded URL separator symbols are NOT decoded when the second
  argument of `urlDecode()` is set to false (which is the default).

src/tools/stringTools.cpp

@@ -172,7 +172,6 @@ bool isReservedUrlChar(char c)
   switch (c) {
   case ';':
   case ',':
-  case '/':
   case '?':
   case ':':
   case '@':
@@ -206,6 +205,7 @@ bool isHarmlessUriChar(char c)
   case '\'':
   case '(':
   case ')':
+  case '/':
     return true;
   }
   return false;