refs and revparse love <3

examples: add README

Bring back `entry_bypath`

diff: make inter-hunk-context default value git-compliant

Point to the libgit2-glib wiki page

Fix libgit2 on GNU/Hurd.

passing 0 to git_strol(32|64) let the implementation guess if it's
dealing with an octal number or a decimal one.

Let's make it safe and ensure that both 'HEAD@{010}' and 'HEAD@{10}'
point at the same commit.

On GNU, the d_name field of the dirent structure is defined as "char d_name[1]",
so we must allocate more than sizeof(struct dirent) bytes, just like on Sun.

revparse: fix parsing of date specifiers

Replace incorrect 'it' with 'if' in documentation