vector: Timsort all of the things

Drop the GLibc implementation of Merge Sort and replace it with Timsort.

The algorithm has been tuned to work on arrays of pointers (void **),
so there's no longer a need to abstract the byte-width of each element
in the array.

All the comparison callbacks now take pointers-to-elements, not
pointers-to-pointers, so there's now one less level of dereferencing.

E.g.

	 int index_cmp(const void *a, const void *b)
	 {
	-	const git_index_entry *entry_a = *(const git_index_entry **)(a);
	+	const git_index_entry *entry_a = (const git_index_entry *)(a);

The result is up to a 40% speed-up when sorting vectors. Memory usage
remains lineal.

A new `bsearch` implementation has been added, whose callback also
supplies pointer-to-elements, to uniform the Vector API again.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/tree.c b/src/tree.c
index 51b19f535..fff5068f8 100644
--- a/src/tree.c
+++ b/src/tree.c
@@ -40,7 +40,7 @@ static int valid_attributes(const int attributes) {
 int entry_search_cmp(const void *key, const void *array_member)
 {
 	const char *filename = (const char *)key;
-	const git_tree_entry *entry = *(const git_tree_entry **)(array_member);
+	const git_tree_entry *entry = (const git_tree_entry *)(array_member);
 
 	return strcmp(filename, entry->filename);
 }
@@ -53,8 +53,8 @@ static int valid_attributes(const int attributes) {
 
 int entry_sort_cmp(const void *a, const void *b)
 {
-	const git_tree_entry *entry_a = *(const git_tree_entry **)(a);
-	const git_tree_entry *entry_b = *(const git_tree_entry **)(b);
+	const git_tree_entry *entry_a = (const git_tree_entry *)(a);
+	const git_tree_entry *entry_b = (const git_tree_entry *)(b);
 
 	return git_futils_cmp_path(entry_a->filename, strlen(entry_a->filename),
                                   entry_a->attr & 040000,