Allow maximum-issues to be set via command-line

This change allows the maximum issues to be passed in as an argument.
If nothing is passed, then the existing build-in maximum is
used.

Retaining the existing built-in value makes sense for home
users to keep track of their local build (otherwise they would have
to remember the prior number of warnings and pass that value
in for subsequent builds).

Motivation: until now the built-in maximum covers the build permutation
that happens to generate the most warnings versus other builds.
In some cases new warnings may not be cause if they elicit a warning
from the lesser-warning build(s) or compilers, but not in the
maximum-warning build.

This change lets us tighten-down the warning uniquely for each build,
so we can be sure all new warnings are flagged to the developer.

.pylint

@@ -138,7 +138,8 @@ disable=print-statement,
         xreadlines-attribute,
         deprecated-sys-function,
         exception-escape,
-        comprehension-escape
+        comprehension-escape,
+        duplicate-code
 
 # Enable the message, report, category or checker with the given id(s). You can
 # either give multiple identifier separated by comma (,) or put this option