Avoid symbol collision with aklomp/base64

In static builds, symbol collisions are possible since the functions are
named the same.

Embed the base64 library in the only file where it's used and make all
its functions static.

Author: saghul

CMakeLists.txt

@@ -95,8 +95,7 @@ add_custom_target(gen_jwt_checker ALL DEPENDS jwt-checker.i)
 add_dependencies(jwt        gen_jwt_builder gen_jwt_checker)
 add_dependencies(jwt_static gen_jwt_builder gen_jwt_checker)
 
-set(JWT_SOURCES libjwt/base64.c
-	libjwt/jwt-memory.c
+set(JWT_SOURCES libjwt/jwt-memory.c
 	libjwt/jwt.c
 	libjwt/jwks.c
 	libjwt/jwt-setget.c

libjwt/base64.c

@@ -12,8 +12,6 @@
 
 #include <jwt.h>
 
-#include "base64.h"
-
 #include "jwt-private.h"
 
 static int write_js(const json_t *js, char **buf)