Log Message:
Updated mbone/rtptools to 1.21
------------------------------
1.21 (July 2016)
    Yann E. MORIN (yann.morin.1998@free.fr): Buildroot [1] is a build-system
    targetting embedded devices. It is able to build toolchains for various
    architectures, based on the traditional GNU compiler collection gcc, the GNU
    binutils and various C libraries, such as GNU libc (glibc), uClibc [2] [3] or
    musl [4].

    glibc is a feature-full C library, which has had support for Yellow Pages
    (and the rest of the SUN RPC stuff) for a long time. However, circa the 2.14
    release, glibc stopped installing the RPC headers [5], on the principle that
    providing the RPC implementation would be better served by a third-party
    package, namely ti-rpc [6]. That did not happen in time, so installing the
    RPC headers from glibc was re-instated circa 2.16.

    uClibc (no longer maintained, replaced by a fork, uClibc-ng) is a fully
    configurable C library for embedded systems. It entirely lacks a SUN RPC
    implementation altogether.

    musl is standards-conforming, lightweight C library. It also entirely lacks a
    SUN RPC implementation.

    TI-RPC is a stand-alone package. It may or may not be available (because the
    user may not need SUN RPC stuff on an embedded device, for example). Besides,
    it is not yet as feature-full as the implementation in glibc, though for all
    practical means, it is totally useable.

    So, there are cases where a SUN RPC implementation is not available.

    This patch makes it so that the use of Yellow Pages is conditional on the
    presence of a SUN RPC implementation, by checking at ./configure whether the
    required header is present, and disabling the corresponding code if the
    header is missing.

    At the same time, the legacy, long unsupported AM_C_PROTOTYPES directive is
    also removed, as it makes recent-ish autoconf fail.