Warnings JSON with ubuntu

[gbaligh]

json_tokener.c: In function 'json_tokener_do_parse':
json_tokener.c:241:6: warning: pointer targets in passing argument 2 of 'printbuf_memappend' differ in signedness [-Wpointer-sign]
      printbuf_memappend(this->pb, utf_out, 1);
      ^
In file included from json_tokener.c:26:0:
printbuf.h:32:1: note: expected 'char *' but argument is of type 'unsigned char *'
 printbuf_memappend(struct printbuf *p, char *buf, int size);
 ^
json_tokener.c:245:6: warning: pointer targets in passing argument 2 of 'printbuf_memappend' differ in signedness [-Wpointer-sign]
      printbuf_memappend(this->pb, utf_out, 2);
      ^
In file included from json_tokener.c:26:0:
printbuf.h:32:1: note: expected 'char *' but argument is of type 'unsigned char *'
 printbuf_memappend(struct printbuf *p, char *buf, int size);
 ^
json_tokener.c:250:6: warning: pointer targets in passing argument 2 of 'printbuf_memappend' differ in signedness [-Wpointer-sign]
      printbuf_memappend(this->pb, utf_out, 3);
      ^
In file included from json_tokener.c:26:0:
printbuf.h:32:1: note: expected 'char *' but argument is of type 'unsigned char *'
 printbuf_memappend(struct printbuf *p, char *buf, int size);
 ^
json_tokener.c:292:4: warning: 'deemed_double' may be used uninitialized in this function [-Wmaybe-uninitialized]
  if(!deemed_double && sscanf(tmp, "%d", &numi) == 1) {
    ^
json_tokener.c:361:9: warning: 'quote_char' may be used uninitialized in this function [-Wmaybe-uninitialized]
       if(c == quote_char) {