Jemalloc updated to 3.6.0.

Not a single bug in about 3 months, and our previous version was
too old (3.2.0).

deps/jemalloc/test/integration/mremap.c

@@ -0,0 +1,45 @@
+#include "test/jemalloc_test.h"
+
+TEST_BEGIN(test_mremap)
+{
+	int err;
+	size_t sz, lg_chunk, chunksize, i;
+	char *p, *q;
+
+	sz = sizeof(lg_chunk);
+	err = mallctl("opt.lg_chunk", &lg_chunk, &sz, NULL, 0);
+	assert_d_eq(err, 0, "Error in mallctl(): %s", strerror(err));
+	chunksize = ((size_t)1U) << lg_chunk;
+
+	p = (char *)malloc(chunksize);
+	assert_ptr_not_null(p, "malloc(%zu) --> %p", chunksize, p);
+	memset(p, 'a', chunksize);
+
+	q = (char *)realloc(p, chunksize * 2);
+	assert_ptr_not_null(q, "realloc(%p, %zu) --> %p", p, chunksize * 2,
+	    q);
+	for (i = 0; i < chunksize; i++) {
+		assert_c_eq(q[i], 'a',
+		    "realloc() should preserve existing bytes across copies");
+	}
+
+	p = q;
+
+	q = (char *)realloc(p, chunksize);
+	assert_ptr_not_null(q, "realloc(%p, %zu) --> %p", p, chunksize, q);
+	for (i = 0; i < chunksize; i++) {
+		assert_c_eq(q[i], 'a',
+		    "realloc() should preserve existing bytes across copies");
+	}
+
+	free(q);
+}
+TEST_END
+
+int
+main(void)
+{
+
+	return (test(
+	    test_mremap));
+}