Update default branch to main (#602)

Author: myd7349

README.rst

@@ -66,7 +66,7 @@ standard (ISO/IEC 9899).
 How is pycparser licensed?
 --------------------------
 
-`BSD license <https://github.com/eliben/pycparser/blob/master/LICENSE>`_.
+`BSD license <https://github.com/eliben/pycparser/blob/main/LICENSE>`_.
 
 Contact details
 ---------------

SECURITY.md

@@ -4,7 +4,7 @@
 
 Only the latest released version is supported
 (see https://github.com/eliben/pycparser/tags). Updates will be made in
-the `master` branch.
+the `main` branch.
 
 ## Reporting a Vulnerability
 

examples/README.rst

@@ -2,7 +2,7 @@ Run these examples from the root directory of pycparser.
 
 Please note that most realistic C code samples would require running the C
 preprocessor before passing the code to **pycparser**; see the `README file
-<https://github.com/eliben/pycparser/blob/master/README.rst>`_ and
+<https://github.com/eliben/pycparser/blob/main/README.rst>`_ and
 `this blog post
 <https://eli.thegreenplace.net/2015/on-parsing-c-type-declarations-and-fake-headers>`_
 more details.