Building the 7.8.90 pretest on MinGW

[Eli Zaretskii <eliz@gnu.org>]

I've built the pretest using MinGW32.  I found 2 issues: one with
gnulib's time.h (reported to the gnulib list), the other with the
recent changes in tui/.  Specifically, starting "gdb -tui" fails with
this error message:

     Cannot enable the TUI: error opening terminal [TERM=<unset>]

This happens because the recent additions to tui.c make assumptions
about the curses library that don't hold for the MinGW port of
ncurses, e.g. that $TERM must be set.

The patch below fixes this for me.  OK to install it (master and
branch)?

2015-01-15  Eli Zaretskii  <eliz@gnu.org>

	* gdb/tui/tui.c (tui_enable) [__MINGW32__]: If the call to 'newterm'
	fails with the 1st arg NULL, try again with "unknown".  Don't test
	the "cup" capability: it isn't supported by the Windows port of
	ncurses, but the Windows console driver is still capable of
	supporting TUI.


--- gdb/tui/tui.c~0	2015-01-13 14:14:48 +0200
+++ gdb/tui/tui.c	2015-01-15 10:52:01 +0200
@@ -425,6 +425,12 @@ tui_enable (void)
 	error (_("Cannot enable the TUI when output is not a terminal"));
 
       s = newterm (NULL, stdout, stdin);
+#ifdef __MINGW32__
+      /* The MinGW port of ncurses requires $TERM to be unset in order
+	 to activate the Windows console driver.  */
+      if (s == NULL)
+	s = newterm ("unknown", stdout, stdin);
+#endif
       if (s == NULL)
 	{
 	  error (_("Cannot enable the TUI: error opening terminal [TERM=%s]"),
@@ -432,7 +438,9 @@ tui_enable (void)
 	}
       w = stdscr;
 
-      /* Check required terminal capabilities.  */
+      /* Check required terminal capabilities.  The MinGW port of
+	 ncurses does have them, but doesn't expose them through "cup".  */
+#ifndef __MINGW32__
       cap = tigetstr ("cup");
       if (cap == NULL || cap == (char *) -1 || *cap == '\0')
 	{
@@ -442,6 +450,7 @@ tui_enable (void)
 		   "terminal doesn't support cursor addressing [TERM=%s]"),
 		 gdb_getenv_term ());
 	}
+#endif
 
       cbreak ();
       noecho ();