If gethostbyname() fails on platforms with NO_ADDRINFO, the code
leaks the struct addrinfo that was allocated.  This fixes that
(and a number of code formatting issues in that area of code in
src/posix.c).

There were a number of functions assigning their return value to
`error` without much explanation.  I added in some rudimentary
error checking to help flesh out the example.

Also, I reformatted all of the comments down to 80 cols (and in
some cases, slightly updated the wording).

push: fix typo in git_push_finish() doc

Topic/diff tree coverage

push: improve docs on success / failure of git_push_finish

Improve MSVC compiler, linker flags

Add git_push_options, to set packbuilder parallelism

Add FORCE_TEXT check into git_diff_blobs code path

Allow network operations to cancel

`git_diff_blobs` and `git_diff_blob_to_buffer` skip the step
where we check file attributes because they don't have a filename
associated with the data. Unfortunately, this meant they were also
skipping the check for the GIT_DIFF_FORCE_TEXT option and so you
could not force a diff of an apparent binary file.  This adds the
force text check into their code path.

Topic/remote isvalidname

Fix libgit2/libgit2sharp#318

reset: Allow the selective reset of pathspecs

Resolve a remote branch's remote

removed other references to api.html

Merge the push report into the refs to avoid a 3rd network call

diff: Add a callback to notify of diffed files

Fix Windows symlinks

As requested