[fix: vim plugin 'inferior' completion]
[fix: vim plugin 'inferior' completion]

	issue: 'inferior' sub-commands 'bin', 'sym', 'args', 'tty' appeared
		   multiple times in command completion

	reason: vimgdb#inferior#complete() listed those arguments while they
			are already completed through the completion dictionary

	fix: replace vimgdb#inferior#complete() by vimgdb#complete#file() as
		 __nested__ completion function for 'inferior'

jnow-87/vimgdb,jnow-87/vimgdb,jnow-87/vimgdb