Append string(s) to a stralloc
#include <stralloc.h>
int stralloc_catm(stralloc* sa,const char* s, ...);
stralloc_catm appends \0-terminated strings from s... to the end of the string stored in sa, allocating space if necessary, and returns 1. If sa is unallocated, stralloc_catm is the same as stralloc_copym.
If it runs out of memory, stralloc_catm 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.