Merge branch 'bc/gnome-keyring'

Cleanups and tweaks for credential handling to work with ancient versions
of the gnome-keyring library that are still in use.

* bc/gnome-keyring:
  contrib/git-credential-gnome-keyring.c: support really ancient gnome-keyring
  contrib/git-credential-gnome-keyring.c: support ancient gnome-keyring
  contrib/git-credential-gnome-keyring.c: report failure to store password
  contrib/git-credential-gnome-keyring.c: use glib messaging functions
  contrib/git-credential-gnome-keyring.c: use glib memory allocation functions
  contrib/git-credential-gnome-keyring.c: use secure memory for reading passwords
  contrib/git-credential-gnome-keyring.c: use secure memory functions for passwds
  contrib/git-credential-gnome-keyring.c: use gnome helpers in keyring_object()
  contrib/git-credential-gnome-keyring.c: set Gnome application name
  contrib/git-credential-gnome-keyring.c: ensure buffer is non-empty before accessing
  contrib/git-credential-gnome-keyring.c: strlen() returns size_t, not ssize_t
  contrib/git-credential-gnome-keyring.c: exit non-zero when called incorrectly
  contrib/git-credential-gnome-keyring.c: add static where applicable
  contrib/git-credential-gnome-keyring.c: *style* use "if ()" not "if()" etc.
  contrib/git-credential-gnome-keyring.c: remove unused die() function
  contrib/git-credential-gnome-keyring.c: remove unnecessary pre-declarations