Option to NOT force libc++ when building with clang (#4826)

Option to NOT force libc++ when building with clang (#4826)

* Eclipse ignore

* TypeScript support

* Prefixing enums

* Test results

* Merged JS and TS generators

* Fixed AppVeyor build problems

* Fixed more AppVeyor build problems

* Fixed more AppVeyor build problems

* Changed TS flag to options struct

* Storing options by value

* Removed unneeded const

* Re-export support for unions

* Uint support

* Casting bools to numbers for mutation

* TS shell tests

* Reverted generates js test file to original version

* Backing up js tests and properly generating test data

* Not importing flatbuffers for TS test generation

* Not overwriting generated js for tests

* AppVeyor test fixes

* Generating the most strict TS code possible

* Not returning null when creating vectors

* Not returning null from struct contructors

* Vector of unions for ts/js

* Sanity check for languages

* Indentation fix + output test files

* Vectors of unions for php

* Fixes to union vector handling + tests

* Fix for strictPropertyInitialization

* Fix for new aligned operator new for gcc >= 7.1

* Not generating imports/ns prefixes with --gen-all

* TypeScript docs

* Missing imports of enums

* Missing TS links

* Enabled vector of unions for java, since it seems to work

* Added jitpack config

* Added obj to vector of unions getter

* Removed unneeded accessor

* Bumped jdk version in pom.xml

* Vector of unions support for c#

* Missing TypeScript doc processing

* Option to NOT force libc++ when building with clang