pmemblk, dev-dax: load libpmem and libpmemblk at startup

pmemblk, dev-dax: load libpmem and libpmemblk at startup

The pmemblk and dev-dax ioengines were loading libpmem.so and
libpmemblk.so using dlopen() at runtime.

Although the upstream nvml Makefile installs a libpmem.so
symbolic link, some of the distros (e.g. SUSE Linux Enterprise
Server 12 SP2) are just installing so.1 symbolic links.  So,
fio fails to find the libpmem.so and libpmemblk.so library files.

http://www.ibm.com/developerworks/linux/library/l-shlibs/index.html
says applications should always load the versioned filenames to
avoid compatibility issues; the non-versioned filenames are just
for the compiler and linker.

Change ./configure to pass -lpmem and -lpmemblk to the compiler
so the fio binary loads the versioned filename at startup like
the other libraries, rather than open the non-versioned filename
with dlopen() during runtime.

This way they show up in ldd:
$ ldd fio
        linux-vdso.so.1 (0x00007ffc290aa000)
        libpmemblk.so.1 => /lib64/libpmemblk.so.1 (0x00007f65b5bc4000)
        libpmem.so.1 => /lib64/libpmem.so.1 (0x00007f65b59be000)
        libnuma.so.1 => /lib64/libnuma.so.1 (0x00007f65b57b3000)
        librt.so.1 => /lib64/librt.so.1 (0x00007f65b55ab000)
        libaio.so.1 => /lib64/libaio.so.1 (0x00007f65b53a9000)
        libz.so.1 => /lib64/libz.so.1 (0x00007f65b5191000)
        libm.so.6 => /lib64/libm.so.6 (0x00007f65b4e88000)
        libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f65b4c6a000)
        libdl.so.2 => /lib64/libdl.so.2 (0x00007f65b4a66000)
        libc.so.6 => /lib64/libc.so.6 (0x00007f65b46a0000)
        libuuid.so.1 => /lib64/libuuid.so.1 (0x00007f65b449b000)
        /lib64/ld-linux-x86-64.so.2 (0x0000559f4d872000)

Signed-off-by: Jens Axboe <axboe@fb.com>