Append data to a stralloc
#include <stralloc.h>
int stralloc_cat(stralloc* sato,stralloc* safrom);
stralloc_cat appends the string stored in safrom to sa. It is the same as stralloc_catb(&sato, safrom.s, safrom.len). safrom must already be allocated.
The data that sa previously contained is overwritten and truncated.
1 for success, 0 on memory allocation failure.