MakeMaker.pm: do not use Makefile.embed to build libgit2 to avoid FTBFS on *BSD
xs: update libgit2
Changes: update
Raw.xs: update git_cred_acquire_cbb() signature
MakeMaker.pm: fix SSL support
v0.21

 - Reference -> target(), Tree -> diff() and TreeEntry -> object() methods do
   not accept a Repository argument anymore (incompatible change)
 - Fix memory leak in Tree -> entry_bypath() (GH#11)
 - Tag -> delete() is now an object method just like other delete() methods
   (incompatible change)
 - Do not use Makefile.embed to build libgit2 to avoid FTBFS on *BSD
 - Update libgit2 to fd69c7b
99-clean.t: remove test_repo after tests, to allow 'make test' to run multiple times
xs: update libgit2
MakeMaker.pm: pass -Wall to CFLAGS
Raw.xs: pass class to Branch and Tag foreach callbacks
xs: fix various warnings
Changes: update
v0.22

 - Remove test_repo after tests, to allow "make test" to run multiple times
   (should fix OpenBSD CPAN Testers)
 - Update libgit2 to 5eeb357