Compiling with the flang compiler

[nncarlson]

This issue tracks the status of compiling petaca using the flang compiler, which is currently not working.

You should use the flang branch, which contains additions, workarounds, etc. for the compiler. I periodically rebase it onto the master branch (bad practice, I know -- sorry).

[nncarlson]

Using the March 2019 binary release, these are the failing tests:

The following tests FAILED:
	  4 - any_vector (Failed)
	  5 - any_matrix (Failed)
	  6 - parameter_list (SEGFAULT)
	  7 - parameter_list_json (Failed)

Workarounds for several serious compiler bugs were required to get to this point, including:

• Wrong assignment of structure with CLASS(*) allocatable component flang-compiler/flang#244 -- intrinsic assignment of types with class(*) component does not work.
• Wrong result from MOVE_ALLOC with character variables flang-compiler/flang#721 -- move_alloc does not work with character variables
• Sourced allocation of polymorphic with MOLD= does not define type flang-compiler/flang#722 -- allocate with MOLD= does not work

Other compiler bugs with no apparent workaround as of yet are:

• ICE: attempt to get size of assumed size character flang-compiler/flang#713
• Wrong array bounds on CLASS(*) dummy in SELECT TYPE flang-compiler/flang#714
  These involve allocation of a class(*) variable and/or array to a character type. The compiler is severely broken when it comes to this.