vla: print "variable length" for unresolved dynamic bounds

vla: print "variable length" for unresolved dynamic bounds

1| void foo (size_t n) {
2|   int vla[n];
3| }

Given the following expression

  (gdb) ptype &vla

Gdb evaluates the expression with EVAL_AVOID_SIDE_EFFECTS and thus
does not resolve the bounds information and misinterprets the high
bound as a constant. The current output is:

  type = int (*)[1289346]

this patch deals with this case and prints:

  type = int (*)[variable length]

instead.

gdb/ChangeLog:

	* c-typeprint.c (c_type_print_varspec_suffix): Added
	check for not yet resolved high bound. If unresolved, print
	"variable length" string to the console instead of random
	length.