* many bugfixes for js
fixes#12672, fixes#14153, closes#14123, closes#11331, fixes#11783, fixes#13966, fixes#14087, fixes#14117, closes#12256.
mostly fixes the fact that it was allowed to assign to newly created temp variables. additionally attempts to get rid of null initialized seqs/strings (though they might pop up here and there); this simplifies a lot of things and makes code size smaller. even if null seqs/strings pop up here and there it's still better than all those bugs existing.
* formatting fixes
* CI fixes
* more CI fixes
* removed mangling of object fields for the js target only.
* changed default mangling behaviour for the php target as well.
* Added test for unorthodox field names (reserved words and operators). Adjusted field accessors and object constructors / new to be ECMAScript first edition compatible, when using fieldnames which are reserved words.