[libxml2] Allow to select the threading system on Windows

[Daniel Veillard <veillard src gnome org>]

commit 203fd2e6c72984711e8904557046aca0c8ee920c
Author: LRN <lrn1986 google com>
Date:   Fri Aug 7 21:47:25 2009 +0200

    Allow to select the threading system on Windows
    
    * configure.in: changes to enable either pthreads or win32-threads

 configure.in |   26 +++++++++++++++-----------
 1 files changed, 15 insertions(+), 11 deletions(-)
---
diff --git a/configure.in b/configure.in
index 9d64dfd..6c0e139 100644
--- a/configure.in
+++ b/configure.in
@@ -870,17 +870,21 @@ if test "$with_threads" = "no" ; then
     echo Disabling multithreaded support
 else
     echo Enabling multithreaded support
-
-    AC_CHECK_HEADER(pthread.h,
-	AC_CHECK_LIB(pthread, pthread_join,[
-	   THREAD_LIBS="-lpthread"
-	   AC_DEFINE([HAVE_LIBPTHREAD], [], [Define if pthread library is there (-lpthread)])
-	   AC_DEFINE([HAVE_PTHREAD_H], [], [Define if <pthread.h> is there])
-	   WITH_THREADS="1"]))
+    dnl Use pthread by default
+    if test "$with_threads" = "pthread" | test "$with_threads" = "" ; then
+        AC_CHECK_HEADER(pthread.h,
+	    AC_CHECK_LIB(pthread, pthread_join,[
+	       THREAD_LIBS="-lpthread"
+	       AC_DEFINE([HAVE_LIBPTHREAD], [], [Define if pthread library is there (-lpthread)])
+	       AC_DEFINE([HAVE_PTHREAD_H], [], [Define if <pthread.h> is there])
+	       WITH_THREADS="1"]))
+    fi
     case $host_os in
-       *mingw32*) WITH_THREADS="1"
-           THREADS_W32="Win32"
-	   THREAD_CFLAGS="$THREAD_CFLAGS -DHAVE_WIN32_THREADS"
+       *mingw32*) if test "$THREAD_LIBS" != "-lpthread"; then
+               WITH_THREADS="1"
+               THREADS_W32="Win32"
+	       THREAD_CFLAGS="$THREAD_CFLAGS -DHAVE_WIN32_THREADS"
+           fi
        ;;
        *cygwin*) THREAD_LIBS=""
        ;;
@@ -898,7 +902,7 @@ else
 		       THREAD_LIBS=""
 		       BASE_THREAD_LIBS="-lpthread"
 		   else
-		   if expr ${GCC_MAJOR} \> 3 > /dev/null 
+		   if expr ${GCC_MAJOR} \> 3 > /dev/null
 		   then
 		       THREAD_LIBS=""
 		       BASE_THREAD_LIBS="-lpthread"