Description of problem:
libmemcached fails to link libpthread. In RHEL 7, libmemcached doesn't have dependency on libpthread as compared with older RHEL versions.

Version-Release number of selected component (if applicable):
Red Hat Enterprise Linux 7.0
libmemcached-1.0.16-3.el7.x86_64

How reproducible:
Always

Steps to Reproduce:
1.# cat > test.c
#include <libmemcached/memcached.h>

int main()
{
	memcached_st ms;
	memcached_create(&ms);
        return 0;
}

2. # gcc -Wall -o test test.c -lmemcached
/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../lib64/libmemcached.so: undefined reference to `pthread_once'
collect2: error: ld returned 1 exit status

Actual results:
Program throws a linker error.

Expected results:
Fix linking against libpthread. Program should build without any link errors. 

Additional info:
RHEL 7 :
# ldd /usr/lib64/libmemcached.so
	linux-vdso.so.1 =>  (0x00007fff985fe000)
	libdl.so.2 => /lib64/libdl.so.2 (0x00007fce89122000)
	libsasl2.so.3 => /lib64/libsasl2.so.3 (0x00007fce88f05000)
	libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007fce88bfd000)
	libm.so.6 => /lib64/libm.so.6 (0x00007fce888fb000)
	libc.so.6 => /lib64/libc.so.6 (0x00007fce8853a000)
	libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007fce88323000)
	/lib64/ld-linux-x86-64.so.2 (0x00007fce8956c000)
	libresolv.so.2 => /lib64/libresolv.so.2 (0x00007fce88109000)
	libcrypt.so.1 => /lib64/libcrypt.so.1 (0x00007fce87ed2000)
	libfreebl3.so => /lib64/libfreebl3.so (0x00007fce87c52000)

RHEL 6 :
# ldd /usr/lib64/libmemcached.so
	linux-vdso.so.1 =>  (0x00007fff4dbf4000)
	libm.so.6 => /lib64/libm.so.6 (0x00007fe1a3be7000)
	libpthread.so.0 => /lib64/libpthread.so.0 (0x00007fe1a39ca000)  <--====
	libc.so.6 => /lib64/libc.so.6 (0x00007fe1a3635000)
	/lib64/ld-linux-x86-64.so.2 (0x0000003379e00000)

Workaround :
# gcc -Wall -o test test.c -lmemcached -lpthread

Fedora BZ : https://bugzilla.redhat.com/show_bug.cgi?id=1037707
A patch is provided in above BZ which fixes this issue. (patch attached to bug report).