code: relax max line length to 120

CODING_CONVENTIONS.md

@@ -11,7 +11,7 @@
   https://www.kernel.org/doc/Documentation/process/coding-style.rst with the
   following modifications and additions:
     * Line length: aim for no more than 80 characters per line, the absolute
-      maximum should be 100 characters per line.
+      maximum should be 120 characters per line.
     * All line endings shall be set to LF (`\n`). (How to handle line endings in
       Git: https://help.github.com/articles/dealing-with-line-endings)
     * There must be no trailing whitespace in any line.

CODING_CONVENTIONS_C++.md

@@ -127,10 +127,10 @@ void my_class::do_something_else() {
 
 - Use 4 spaces per indentation level.
 
-- The maximum number of characters per line is 80.
-
 - No tabs, ever.
 
+- Aim for 80 characters per line, and do not exceed a maximum of 120.
+
 - Never use C-style casts.
 
 - Vertical whitespaces separate functions and are not used inside functions:

dist/tools/vera++/profiles/riot_force_params.txt

@@ -1,2 +1,2 @@
-max-line-length=100
+max-line-length=120
 max-consecutive-empty-lines=1