patch 9.1.1794: configure: terminfo test does not work with musl

Problem:  configure: terminfo test does not work with musl
          (T3rm1, after v9.9.1.0837)
Solution: include term.h in configure script, add forward declarations,
          in case headers are not found

fixes: #18393
closes: #18405

Signed-off-by: Christian Brabandt <cb@256bit.org>

src/auto/configure

@@ -13547,8 +13547,13 @@ else case e in #(
 /* end confdefs.h.  */
 
 #include "confdefs.h"
-#ifdef HAVE_TERMCAP_H
+#ifdef HAVE_TERM_H
+# include <term.h>
+#elif defined(HAVE_TERMCAP_H)
 # include <termcap.h>
+#else
+  /* forward declare tgoto */
+  extern char *tgoto(const char *, int, int);
 #endif
 #ifdef HAVE_STRING_H
 # include <string.h>

src/configure.ac

@@ -3651,8 +3651,13 @@ AC_CACHE_CHECK([whether we talk terminfo], [vim_cv_terminfo],
   [
     AC_RUN_IFELSE([AC_LANG_SOURCE([[
 #include "confdefs.h"
-#ifdef HAVE_TERMCAP_H
+#ifdef HAVE_TERM_H
+# include <term.h>
+#elif defined(HAVE_TERMCAP_H)
 # include <termcap.h>
+#else
+  /* forward declare tgoto */
+  extern char *tgoto(const char *, int, int);
 #endif
 #ifdef HAVE_STRING_H
 # include <string.h>

src/version.c

@@ -729,6 +729,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1794,
 /**/
     1793,
 /**/