mmap.c (backtrace_free): If freeing a large aligned block of memory, call munmap rather than holding onto it.

	* mmap.c (backtrace_free): If freeing a large aligned block of
	memory, call munmap rather than holding onto it.
	(backtrace_vector_grow): When growing a vector, double the number
	of pages requested.  When releasing the old version of a grown
	vector, pass the correct size to backtrace_free.

From-SVN: r210256