Bump libgit2 to 43275f512ef888a14c43bde8007251ce595be32a + unmerged proxy fixes

[srajko]

No description provided.

[rcjsuen]

Bumping libgit2 to master would also fix #1220. Keep in mind though that things are a little fishy there since the test suite crashes but the builds are green...

[srajko]

@rcjsuen in which builds are you seeing the tests crash?

[rcjsuen]

@srajko Take a look at the AppVeyor and Travis CI builds that got spawned off for #1220. While AppVeyor is correctly red, Travis CI is green even though the test suite has segfaulted... :(

[srajko]

That is indeed fishy :-) Thanks for pointing that out, definitely something we should resolve.

[tommoor]

0.17.0 is also crashing our test suites, I'm not sure why as karma disconnects with no result - subscribing to this in the hope that this will fix our woes when merged!

[johnhaley81]

@srajko this needs a rebase now :(

[johnhaley81]

Well, everything is green except for the 32-bit linux builds which aren't really related to this PR and are fixed in #1241 so I'll admin merge this. Thanks @srajko

[johnhaley81]

Included merged libgit2 PRs:

• Use a shared buffer in calls of git_treebuilder_write to avoid heap contention #3892
• WinHTTP: set proper error messages when SSL fails #4050
• Clang analyzer run #4051
• Extend packfile in increments of page_size. #4053
• Fix general example memory leaks #4078
• WIP: some coverity & compiler warning fixes #4086
• Fix a few recent warnings #4087
• Fix uninitialized variable warning #4095
• Update docs for git_oid_fromstrn and p #4096
• Fix digest credentials for proxy in windows #4104
• Vector reverse overflow #4105
• Flag given_opts in git_revert as optional #4108
• Flag checkout_opts in git_reset as optional #4109
• dirname with DOS prefixes #4111
• Add support for lowercase proxy environment variables #4112
• Flag options in git_stash_apply and git_stash_pop as being optional #4117
• rename detection: don't try to detect submodule renames #4119
• tests: fix permissions on testrepo.git index file #4121

Included non-merged libgit2 PRs:

• negotiate always fails via libcurl #4126
• Fix proxy auto detect not utilizing callbacks #4097

Both of which are proxy related.