Copy string(s) to a stralloc
#include <stralloc.h>
int stralloc_copym(stralloc* sa,const char* s, ...);
stralloc_cats copies \0-terminated strings from s... to sa, allocating space if necessary, and returns 1. If there is data in the sa, it is cleared first.
If it runs out of memory, stralloc_copym returns 0. At that point, it may already have copied a few of the strings to sa.
1 for success, 0 on memory allocation failure.