Clean up whitespace. Lock access of swap_avail when printing stats. Use inttypes.h for portable printf() format specifiers, specifically for uint64_t (PRIu64). Change highchunks and curchunks stats from (unsigned long) to (size_t).
Add the w4opaque argument malloc_message() and malloc_stats_print(), and propagate the change through all the internal APIs as necessary.
Fix some bugs in the Makefile's install target.