libpq: Add missing file to GETTEXT_FILES list

For the record, fe-print.c is also missing, but it's sort of
deprecated, and the string internationalization there has some issues,
and it doesn't seem worth fixing that.  So let's leave that out.

src/interfaces/libpq/nls.mk

 # src/interfaces/libpq/nls.mk
 CATALOG_NAME     = libpq
 AVAIL_LANGUAGES  = cs de es fr it ja ko pt_BR ru sv ta tr zh_CN zh_TW
-GETTEXT_FILES    = fe-auth.c fe-connect.c fe-exec.c fe-lobj.c fe-misc.c fe-protocol2.c fe-protocol3.c fe-secure.c
+GETTEXT_FILES    = fe-auth.c fe-connect.c fe-exec.c fe-lobj.c fe-misc.c fe-protocol2.c fe-protocol3.c fe-secure.c win32.c
 GETTEXT_TRIGGERS = libpq_gettext pqInternalNotice:2
 GETTEXT_FLAGS    = libpq_gettext:1:pass-c-format pqInternalNotice:2:c-format