gcc: update to 4.9.4, mpfr update to 3.1.4, gmp update to 6.1.1 * src/build-gcc.mk: update version, checksum * src/gmp.mk: update version, checksum * src/mpfr.mk: update version, checksum * src/native-gcc.mk: update version, checksum

#include <iostream>
#include <cpp/poppler-version.h>

int main(int argc, char *argv[])
{
    (void)argc;
    (void)argv;

    std::cout << "Poppler version: " << poppler::version_string() << std::endl;

    return 0;
}