IDL compiler: [EnabledAtRuntime] attributes

Python CG code mostly there already, since [EnabledAtRuntime] already used for constants.
Perl has a notion of '@normalAttributes', but for now I'm explicitly
listing the conditions (not static, not [EnabledAtRuntime])
in the template to avoid added abstraction.

Also some Perl CG changes (linebreaks) to simplify the Jinja template.
Only fanciness is a special filter to indent, skipping blank lines and
preprocessor directives.
(Simplifies Jinja template b/c don't need to indent and unident in macros.)

https://sites.google.com/a/chromium.org/dev/blink/webidl/blink-idl-extended-attributes#TOC-EnabledAtRuntime-i-m-a-p-

BUG=239771
NOTRY=true

Review URL: https://codereview.chromium.org/26650002

git-svn-id: svn://svn.chromium.org/blink/trunk@159617 bbb929c8-8fbe-4397-9dbb-9b2b20218538