Debian packaging: add pkg-config to Build-Depends and bump to 1.5.1
remove copy/pasted comments
support 3rd-party initiated login as defined in the spec

see: http://openid.net/specs/openid-connect-core-1_0.html
section: 4.  Initiating Login from a Third Party
add test.c to distfiles
leave out test from distrfiles for now

needs libapr detection first
release 1.5.1