Patch 775605: Cygwin pthread_sigmask() workaround patch

Cygwin's pthread_sigmask() implementation appears to be buggy. This
patch works around this problem by using sigprocmask() instead.

This patch is implemented in a general way so it could be used by other
platforms too. If this approach is deemed too risky, then I can work up
a patch that just hacks Python/thread_pthread.h for Cygwin.

Note that I tested this patch against 2.3c1 under Red Hat Linux 8.0 too.

[snip]
And finally, I need someone to regenerate pyconfig.h.in and configure
with the same versions of the autotools that are normally used by
Python.

Neal kindly regenerated pyconfig.h.in and configure for me.
diff --git a/configure b/configure
index a132a9e..d067edd 100755
--- a/configure
+++ b/configure
@@ -1,5 +1,5 @@
 #! /bin/sh
-# From configure.in Revision: 1.424 .
+# From configure.in Revision: 1.425 .
 # Guess values for system-dependent variables and create Makefiles.
 # Generated by GNU Autoconf 2.53 for python 2.3.
 #
@@ -908,7 +908,7 @@
 # Don't blindly perform a `cd "$ac_dir"/$ac_foo && pwd` since $ac_foo can be
 # absolute.
 ac_abs_builddir=`cd "$ac_dir" && cd $ac_builddir && pwd`
-ac_abs_top_builddir=`cd "$ac_dir" && cd ${ac_top_builddir}. && pwd`
+ac_abs_top_builddir=`cd "$ac_dir" && cd $ac_top_builddir && pwd`
 ac_abs_srcdir=`cd "$ac_dir" && cd $ac_srcdir && pwd`
 ac_abs_top_srcdir=`cd "$ac_dir" && cd $ac_top_srcdir && pwd`
 
@@ -11785,7 +11785,15 @@
   cat >>confdefs.h <<_ACEOF
 #define `echo "HAVE_$ac_func" | $as_tr_cpp` 1
 _ACEOF
+ case $ac_sys_system in
+        CYGWIN*)
 
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_BROKEN_PTHREAD_SIGMASK 1
+_ACEOF
+
+            ;;
+        esac
 fi
 done
 
@@ -18502,7 +18510,7 @@
 # Don't blindly perform a `cd "$ac_dir"/$ac_foo && pwd` since $ac_foo can be
 # absolute.
 ac_abs_builddir=`cd "$ac_dir" && cd $ac_builddir && pwd`
-ac_abs_top_builddir=`cd "$ac_dir" && cd ${ac_top_builddir}. && pwd`
+ac_abs_top_builddir=`cd "$ac_dir" && cd $ac_top_builddir && pwd`
 ac_abs_srcdir=`cd "$ac_dir" && cd $ac_srcdir && pwd`
 ac_abs_top_srcdir=`cd "$ac_dir" && cd $ac_top_srcdir && pwd`