patch 9.1.0508: termdebug plugin can be further improved

Problem:  termdebug plugin can be further improved
Solution: add sanity-check, timeout config, change vars to bool
          update docs, add more tests (Ubaldo Tiberi)

fixes: #15061
closes: #15057

Signed-off-by: Ubaldo Tiberi <ubaldo.tiberi@google.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/terminal.txt b/runtime/doc/terminal.txt
index 83c8793..5058bf0 100644
--- a/runtime/doc/terminal.txt
+++ b/runtime/doc/terminal.txt
@@ -1,4 +1,4 @@
-*terminal.txt*	For Vim version 9.1.  Last change: 2024 Jun 18
+*terminal.txt*	For Vim version 9.1.  Last change: 2024 Jun 20
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -1283,6 +1283,15 @@
 opened windows are closed.
 
 Only one debugger can be active at a time.
+
+						*termdebug-timeout*
+Depending on how gdb is launched, termdebug startup time may vary.
+To avoid termdebug to get stuck if the startup process of gdb takes too long,
+a configurable timeout is included. Such time out is configurable in terms of
+multiple of 10ms: >
+    let g:termdebug_config['timeout'] = 500 # 500 * 10ms = 5 seconds.
+
+The default timeout is 3000 ms.
 							*:TermdebugCommand*
 If you want to give specific commands to the command being debugged, you can
 use the `:TermdebugCommand` command followed by the command name and