libpam-radius-auth: new package

libpam-radius-auth: new package

[Thomas:
  - make libpam-radius-auth depend on linux-pam (since it's a
    linux-pam plugin, it needs some header files from linux-pam) by
    adding a "if BR2_PACKAGE_LINUX_PAM...endif" block in
    package/Config.in. This way, we will be grouping all the Linux PAM
    plugins together.
  - Fix the indententation in the Config.in file.
  - Use a better Config.in help text, copy/pasted from the website.
  - Use a tarball instead of github. This allows to remove
    AUTORECONF=YES.
  - Add linux-pam as a dependency.
  - Use $(TARGET_CONFIGURE_OPTS) instead of passing just CC/LD, but
    pass it in the environment rather than as options so that the
    CFLAGS/LDFLAGS added by the package Makefile are still taken into
    account.
  - Use mkdir -p + cp -dpfr instead of $(INSTALL) -D since we are
    copying multiple files.
  - Add a hash file.]

Signed-off-by: Giovanni Zantedeschi <giovanni.zantedeschi@datacom.ind.br>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>