Move jsonsl and wildmat to third-party (#4402)

* Move jsonsl to third-party

This treats it as proper 3rd-party code to which our warning and style
settings don't extend.

* Move wildmat to third-party

This treats it as proper 3rd-party code to which our warning and style
settings don't extend.

* Fixup Xcode project to match new project structure

libtransmission/utils.cc

@@ -42,6 +42,7 @@
 #include <fmt/format.h>
 
 #include <fast_float/fast_float.h>
+#include <wildmat.h>
 
 #include "transmission.h"
 
@@ -193,11 +194,6 @@ size_t tr_strvToBuf(std::string_view src, char* buf, size_t buflen)
     return len;
 }
 
-extern "C"
-{
-    int DoMatch(char const* text, char const* p);
-}
-
 /* User-level routine. returns whether or not 'text' and 'p' matched */
 bool tr_wildmat(std::string_view text, std::string_view pattern)
 {