Cleanup misc.

Regarding debugger.txt (which was Spotted by @Hettomei):
The third section was empty, and the second section is very outdated.
Nvim doesn't have things like Balloon Evalutation and Sun Visual
workshop integration, so just remove the section.

Regarding everything else:
- term.[ch] and term_defs.h don't exist anymore, so remove refs to them
- Add ttybuiltin to vim_diff.txt. It should have been done before, but
  vim_diff.txt didn't exist when ttybuiltin was removed (done in
  3baba1e7bc6698e6bc9f1d37fce88b30d6274bc9,)

Helped-by: Justin M. Keyes <justinkz@gmail.com>

2 files changed, 1 insertions, 11 deletions

diff --git a/src/nvim/keymap.h b/src/nvim/keymap.h
index c82a95c00c..e6fcb4d1d2 100644
--- a/src/nvim/keymap.h
+++ b/src/nvim/keymap.h
@@ -16,7 +16,7 @@
 
 /*
  * For MSDOS some keys produce codes larger than 0xff. They are split into two
- * chars, the first one is K_NUL (same value used in term_defs.h).
+ * chars, the first one is K_NUL.
  */
 #define K_NUL                   (0xce)  /* for MSDOS: special key follows */
 
diff --git a/src/nvim/screen.c b/src/nvim/screen.c
index 8b47d090d4..4442e7bba6 100644
--- a/src/nvim/screen.c
+++ b/src/nvim/screen.c
@@ -6448,11 +6448,6 @@ int screen_ins_lines (
   int j;
   unsigned temp;
 
-  // FAIL if
-  // - there is no valid screen
-  // - the screen has to be redrawn completely
-  // - the line count is less than one
-  // - the line count is more than 'ttyscroll'
   if (!screen_valid(TRUE) || line_count <= 0) {
     return FAIL;
   }
@@ -6507,11 +6502,6 @@ int screen_del_lines (
   int i;
   unsigned temp;
 
-  // FAIL if
-  // - there is no valid screen
-  // - the screen has to be redrawn completely
-  // - the line count is less than one
-  // - the line count is more than 'ttyscroll'
   if (!screen_valid(TRUE) || line_count <= 0) {
     return FAIL;
   }