Issue #3956

There were two issues:

1. Github flavored markdown calls Objective C `objective-c`
2. The gfm.js mode didn't include `-` in its fenced code block regex

Additionally, test/index.html did not import the mode/meta.js file,
which prevented mode lookup by name from working in unit tests.

Issue #3941

Issue #3932

BUCK, BUILD, *.BUILD and *.bzl files are build files for the three build
systems mentioned, and they are all valid Python files.

5.13.4 was a trivial release restoring a LICENSE file.

Issue #3938

Closes #3934

Closes #3922

Closes #3920

Closes #3914

The 6 "n"s are reported as suspicious code by Closure Compiler.
They can just be empty statements instead.

This eliminates a warning from Closure Compiler.

The Error after the while(true) loop is not reachable and should
be removed. The "this.iterator" property should be given an
initial value of 0. This fixes two warnings reported by Closure
Compiler.

Issue #3911

Added tests and fixed some issues uncovered by testing.

corrected angle bracket matching in operators (fixes block comments)
corrected digit matching regex
corrected spelling of 'identifier' in grammar dictionary
notCharacterOrDash explicitly includes lowercase characters
improved variable matching
splatted variables now match
bare '$' and '@' are errors, not variables
moved single-quoted string processing into tokenSingleQuoteString
incomplete strings are errors now
empty strings are no longer errors
added support for here-string interpolation with nesting support
added highlighting for splatted vars
removed arbitrary stream advancement prior to default error in tokenBase
enabled folding braces

The code.google.com link is deprecated. Also add that CodeMirror
is being used as Gerrit's inline editor.

cm.save() might not exist if CodeMirror is not created from a
textarea. This adds an additional check to prevent TypeErrors.

Closes #3905