STABS emitter: Emit proper stabs directive for returning to main file

http://www.freebasic.net/forum/viewtopic.php?f=3&t=22463
ASM backend: Check for extern/dynamic before checking for initializer

It makes more sense this way - and matches the C backend.
STABS emitter: Some clean up for edbgEmitGlobalVar()
STABS emitter: Emit correct type for array descriptors