monkey: new package

Monkey is a small, fast and lightweight open source Web Server for
GNU/Linux.  It has been designed with focus in embedded devices,
therefore its scalable by nature having a low memory and CPU
consumption and an excellent performance.

[Thomas:
  - Add missing dependency on !BR2_STATIC_LIBS (the source code uses
    dlopen) and BR2_USE_MMU (the source code uses fork)
  - Slightly adjust/reword the description of the
    BR2_PACKAGE_MONKEY_SHARED option.
  - Remove all the complicated installation logic for the target, and
    just use "make install" instead.
  - Pass --no-backtrace when uClibc is used, otherwise the build fails
    because <execinfo.h> is not available in uClibc.
  - Pass $(TARGET_CONFIGURE_OPTS) in the environment of the configure
    script., otherwise monkey gets built for the host and not for the
    target.
  - Add a post install target hook to remove a broken symlink
    libmonkey.so installed by Monkey's Makefile when the shared
    library is not enabled.
  - Use TARGET_MAKE_ENV when calling make, just because we should.
  - Pass --malloc-libc so that the libc malloc() is used instead of
    the builtin jemalloc allocator, which requires more work to
    cross-compile properly.
  - Add missing empty line after the .mk header and before the first
    variable definition.]

Signed-off-by: Julien Corjon <corjon.j@ecagroup.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>