patch 8.0.0587: configure check for return value of tgetent skipped

Problem:    Configure check for return value of tgetent is skipped.
Solution:   Always perform the check. (Marvin Schmidt, closes #1664)
diff --git a/src/auto/configure b/src/auto/configure
index e9c2c34..6dd5bb9 100755
--- a/src/auto/configure
+++ b/src/auto/configure
@@ -11506,16 +11506,15 @@
 
 fi
 
-if test "x$olibs" != "x$LIBS"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: checking what tgetent() returns for an unknown terminal" >&5
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking what tgetent() returns for an unknown terminal" >&5
 $as_echo_n "checking what tgetent() returns for an unknown terminal... " >&6; }
 if ${vim_cv_tgent+:} false; then :
   $as_echo_n "(cached) " >&6
 else
 
-      if test "$cross_compiling" = yes; then :
+    if test "$cross_compiling" = yes; then :
 
-	as_fn_error $? "failed to compile test program." "$LINENO" 5
+      as_fn_error $? "failed to compile test program." "$LINENO" 5
 
 else
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
@@ -11535,11 +11534,11 @@
 _ACEOF
 if ac_fn_c_try_run "$LINENO"; then :
 
-	vim_cv_tgent=zero
+      vim_cv_tgent=zero
 
 else
 
-	vim_cv_tgent=non-zero
+      vim_cv_tgent=non-zero
 
 fi
 rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
@@ -11551,10 +11550,9 @@
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $vim_cv_tgent" >&5
 $as_echo "$vim_cv_tgent" >&6; }
 
-  if test "x$vim_cv_tgent" = "xzero" ; then
-    $as_echo "#define TGETENT_ZERO_ERR 0" >>confdefs.h
+if test "x$vim_cv_tgent" = "xzero" ; then
+  $as_echo "#define TGETENT_ZERO_ERR 0" >>confdefs.h
 
-  fi
 fi
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether termcap.h contains ospeed" >&5