Support POSIX semaphores on Linux.
This configure test must run before auto/make, because it adds library.
auto/unix was placed after auto/make just for historical reasons.

Patch by Denis F. Latypoff

auto/configure

diff --git a/auto/configure b/auto/configure
index 8ee1c80..8ef3a9a 100755
--- a/auto/configure
+++ b/auto/configure
@@ -53,6 +53,7 @@
 if [ "$NGX_PLATFORM" != win32 ]; then
     . auto/os/features
     . auto/threads
+    . auto/unix
 fi
 
 . auto/modules
@@ -99,10 +100,6 @@
 . auto/lib/make
 . auto/install
 
-if [ "$NGX_PLATFORM" != win32 ]; then
-    . auto/unix
-fi
-
 # STUB
 . auto/stubs
 

auto/unix

diff --git a/auto/unix b/auto/unix
index 669314b..502c27e 100755
--- a/auto/unix
+++ b/auto/unix
@@ -246,6 +246,19 @@
 . auto/feature
 
 
+if [ $ngx_found = no ]; then
+
+    # Linux has POSIX semaphores in libpthread
+    ngx_feature="POSIX semaphores in libpthread"
+    ngx_feature_libs=-lpthread
+    . auto/feature
+
+    if [ $ngx_found = yes ]; then
+        CORE_LIBS="$CORE_LIBS -lpthread"
+    fi
+fi
+
+
 ngx_feature="struct msghdr.msg_control"
 ngx_feature_name="NGX_HAVE_MSGHDR_MSG_CONTROL"
 ngx_feature_run=no