co_lnotab supports negative line number delta

Issue #26107: The format of the co_lnotab attribute of code objects changes to
support negative line number delta.

Changes:

* assemble_lnotab(): if line number delta is less than -128 or greater than
  127, emit multiple (offset_delta, lineno_delta) in co_lnotab
* update functions decoding co_lnotab to use signed 8-bit integers

  - dis.findlinestarts()
  - PyCode_Addr2Line()
  - _PyCode_CheckLineNumber()
  - frame_setlineno()

* update lnotab_notes.txt
* increase importlib MAGIC_NUMBER to 3361
* document the change in What's New in Python 3.6
* cleanup also PyCode_Optimize() to use better variable names

1 files changed, 1 insertions, 1 deletions

diff --git a/Objects/frameobject.c b/Objects/frameobject.c
index 425a9ee..da2d2ed 100644
--- a/Objects/frameobject.c
+++ b/Objects/frameobject.c
@@ -137,7 +137,7 @@ frame_setlineno(PyFrameObject *f, PyObject* p_new_lineno)
         new_lasti = -1;
         for (offset = 0; offset < lnotab_len; offset += 2) {
             addr += lnotab[offset];
-            line += lnotab[offset+1];
+            line += (signed char)lnotab[offset+1];
             if (line >= new_lineno) {
                 new_lasti = addr;
                 new_lineno = line;