Try to fix python shlib probe for MinGW.

Per discussion with Andrew Dunstan, it seems there are three peculiarities
of the Python installation on MinGW (or at least, of the instance on
buildfarm member frogmouth).  First, the library name doesn't contain
"2.7" but just "27".  It looks like we can deal with that by consulting
get_config_vars('VERSION') to see whether a dot should be used or not.
Second, the library might be in c:/Windows/System32, analogously to it
possibly being in /usr/lib on Unix-oid platforms.  Third, it's apparently
not standard to use the prefix "lib" on the file name.  This patch will
accept files with or without "lib", but the first part of that may well
be dead code.

Author: tglsfdc

config/python.m4

@@ -88,12 +88,18 @@ then
 	found_shlib=1
 else
 	# Otherwise, guess the base name of the shlib.
-	# LDVERSION was added in Python 3.2, before that use $python_version.
+	# LDVERSION was added in Python 3.2, before that use VERSION,
+	# or failing that, $python_version from _PGAC_CHECK_PYTHON_DIRS.
 	python_ldversion=`${PYTHON} -c "import distutils.sysconfig; print(' '.join(filter(None,distutils.sysconfig.get_config_vars('LDVERSION'))))"`
 	if test x"${python_ldversion}" != x""; then
 		ldlibrary="python${python_ldversion}"
 	else
-		ldlibrary="python${python_version}"
+		python_version_var=`${PYTHON} -c "import distutils.sysconfig; print(' '.join(filter(None,distutils.sysconfig.get_config_vars('VERSION'))))"`
+		if test x"${python_version_var}" != x""; then
+			ldlibrary="python${python_version_var}"
+		else
+			ldlibrary="python${python_version}"
+		fi
 	fi
 	# Search for a likely-looking file.
 	found_shlib=0
@@ -124,6 +130,21 @@ else
 			done
 		done
 	fi
+	# As usual, Windows has its own ideas.  c:/Windows/System32 takes the
+	# place of /usr/lib as a possible default library location, and the
+	# "lib" prefix might not be there.
+	if test "$found_shlib" != 1 -a "$PORTNAME" = win32 ; then
+		for d in "${python_libdir}" "${python_configdir}" c:/Windows/System32
+		do
+			for f in "$d/lib${ldlibrary}.dll" "$d/${ldlibrary}.dll" ; do
+				if test -e "$f"; then
+					python_libdir="$d"
+					found_shlib=1
+					break 2
+				fi
+			done
+		done
+	fi
 fi
 if test "$found_shlib" != 1; then
 	AC_MSG_ERROR([could not find shared library for Python

configure

@@ -7631,12 +7631,18 @@ then
 	found_shlib=1
 else
 	# Otherwise, guess the base name of the shlib.
-	# LDVERSION was added in Python 3.2, before that use $python_version.
+	# LDVERSION was added in Python 3.2, before that use VERSION,
+	# or failing that, $python_version from _PGAC_CHECK_PYTHON_DIRS.
 	python_ldversion=`${PYTHON} -c "import distutils.sysconfig; print(' '.join(filter(None,distutils.sysconfig.get_config_vars('LDVERSION'))))"`
 	if test x"${python_ldversion}" != x""; then
 		ldlibrary="python${python_ldversion}"
 	else
-		ldlibrary="python${python_version}"
+		python_version_var=`${PYTHON} -c "import distutils.sysconfig; print(' '.join(filter(None,distutils.sysconfig.get_config_vars('VERSION'))))"`
+		if test x"${python_version_var}" != x""; then
+			ldlibrary="python${python_version_var}"
+		else
+			ldlibrary="python${python_version}"
+		fi
 	fi
 	# Search for a likely-looking file.
 	found_shlib=0
@@ -7667,6 +7673,21 @@ else
 			done
 		done
 	fi
+	# As usual, Windows has its own ideas.  c:/Windows/System32 takes the
+	# place of /usr/lib as a possible default library location, and the
+	# "lib" prefix might not be there.
+	if test "$found_shlib" != 1 -a "$PORTNAME" = win32 ; then
+		for d in "${python_libdir}" "${python_configdir}" c:/Windows/System32
+		do
+			for f in "$d/lib${ldlibrary}.dll" "$d/${ldlibrary}.dll" ; do
+				if test -e "$f"; then
+					python_libdir="$d"
+					found_shlib=1
+					break 2
+				fi
+			done
+		done
+	fi
 fi
 if test "$found_shlib" != 1; then
 	as_fn_error $? "could not find shared library for Python