- remove() would read one-past array bounds.
- resize() would fail if the initial size was 1, because it multiplied by 1.75
  and truncated the resulting value. The buffer would always remain at size 1,
  but elements would repeatedly be appended (via insert()) causing a crash.

The types in the git_index_entry struct are now system-defaults, and get
truncated to uint32_t's when written back on the index.

Signed-off-by: Vicent Marti <tanoku@gmail.com>

All the operations on the 'git_index_entry' array and the
'git_tree_entry' array have been refactored into common code in the
src/vector.c file.

The new vector methods support:
	- insertion:	O(1) (avg)
	- deletion:		O(n)
	- searching:	O(logn)
	- sorting:		O(logn)
	- r. access:	O(1)

Signed-off-by: Vicent Marti <tanoku@gmail.com>