Install properly fe-auth-sasl.h

The internals of the frontend-side callbacks for SASL are visible in
libpq-int.h, but the header was not getting installed.  This would cause
compilation failures for applications playing with the internals of
libpq.

Issue introduced in 9fd8557.

Author: Mikhail Kulagin
Reviewed-by: Jacob Champion
Discussion: https://postgr.es/m/05ce01d777cb$40f31d60$c2d95820$@postgrespro.ru

src/interfaces/libpq/Makefile

@@ -131,6 +131,7 @@ install: all installdirs install-lib
 	$(INSTALL_DATA) $(srcdir)/libpq-fe.h '$(DESTDIR)$(includedir)'
 	$(INSTALL_DATA) $(srcdir)/libpq-events.h '$(DESTDIR)$(includedir)'
 	$(INSTALL_DATA) $(srcdir)/libpq-int.h '$(DESTDIR)$(includedir_internal)'
+	$(INSTALL_DATA) $(srcdir)/fe-auth-sasl.h '$(DESTDIR)$(includedir_internal)'
 	$(INSTALL_DATA) $(srcdir)/pqexpbuffer.h '$(DESTDIR)$(includedir_internal)'
 	$(INSTALL_DATA) $(srcdir)/pg_service.conf.sample '$(DESTDIR)$(datadir)/pg_service.conf.sample'
 
@@ -144,6 +145,7 @@ uninstall: uninstall-lib
 	rm -f '$(DESTDIR)$(includedir)/libpq-fe.h'
 	rm -f '$(DESTDIR)$(includedir)/libpq-events.h'
 	rm -f '$(DESTDIR)$(includedir_internal)/libpq-int.h'
+	rm -f '$(DESTDIR)$(includedir_internal)/fe-auth-sasl.h'
 	rm -f '$(DESTDIR)$(includedir_internal)/pqexpbuffer.h'
 	rm -f '$(DESTDIR)$(datadir)/pg_service.conf.sample'
 

src/tools/msvc/Install.pm

@@ -633,7 +633,8 @@ sub CopyIncludeFiles
 	CopyFiles(
 		'Libpq internal headers',
 		$target . '/include/internal/',
-		'src/interfaces/libpq/', 'libpq-int.h', 'pqexpbuffer.h');
+		'src/interfaces/libpq/', 'libpq-int.h', 'fe-auth-sasl.h',
+		'pqexpbuffer.h');
 
 	CopyFiles(
 		'Internal headers',