Description:
------------
It looks like FreeBSD uses gcc's -pthread switch to specify whether or not something should be linked against a POSIX Threading Library (libpthread|libthr|libc_r) ...

This is apparent e.g. when building libxml2 the generated xml2-config utility (which is used by PHPs build system) gives the following outputfor the --libs target

-L/usr/local/lib -lxml2 -lz -pthread -L/usr/local/lib -liconv -lm

As far as i can tell this data is processed in the PHP_EVAL_LIBLINE m4-macro contained in PHP's acinclude.m4 (passed from ext/xml/config.m4)

And as far as i can tell from the generated configure script it seems to only handle the -l* and -L* entries.

This causes the configure phase for every php-extension that uses -pthread in its library definitions to fail because of missing pthread_* symbols.

Reproduce code:
---------------
Simply try to build any php5-extension module that depends on libxml2 where libxml2 is build with threads-support.

Expected result:
----------------
I expect the configure phase to complete successfully.

Actual result:
--------------
configure:2643: checking whether libxml build works
configure:2672: cc -o conftest -O2 -fno-strict-aliasing -pipe -march=pentium2
conftest.c
          -R/usr/local/lib -L/usr/local/lib -R/usr/local/lib -L/usr/local/lib  -lxml2 -lz -liconv -lm
          >&5
/usr/local/lib/libxml2.so: undefined reference to `pthread_equal'
configure:2675: $? = 1
configure: program exited with status 1
configure: failed program was:
#line 2660 "configure"
#include "confdefs.h"


    char xmlInitParser();
    int main() {
      xmlInitParser();
      return 0;
    }

configure:2696: result: no
configure:2698: error: build test failed.  Please check the config.log for details.