Fix conditions in creating a bitfield.

Fix conditions in creating a bitfield.

Bitfields are represented by intervals [start, begin]. It means that for an
interval comprised by only one  bit start and end will be equal.
The present condition does not always hold. On the other hand in target-description.c
(tdesc_gdb_type) bitfield is created when "f->type" is null. The routine
maint_print_maint_print_c_tdesc_cmd is modified to follow the same strategy.

2013-11-20  Walfred Tedeschi  <walfred.tedeschi@intel.com>

	* target-descriptions.c (maint_print_maint_print_c_tdesc_cmd):
	Modified logic of creating a bitfield to be in sync with
	tdesc_gdb_type.

testsuite/
	* gdb.xml/maint_print_struct.xml (bitfield): Added bitfield having
	start and end equal 0.

Change-Id: I8c62db049995f0c0c30606d9696b86afe237cbb9