C: print the pattern for a #define macro if --excmd=mixed is given

This patch fixes a bug that the pattern for a #define macro is not
printed though --excmd=mixed is given:

Old output:

	$ cat Units/c-define-mixed.d/input.c
	#define X 1
	/* 2 */
	/* 3 */
	/* 4 */
	/* 5 */
	#define Y(v) (6 + v)
	/* 7 */
	$ ctags -o - --excmd=mixed --fields=+n Units/c-define-mixed.d/input.c
	X	Units/c-define-mixed.d/input.c	1;"	d	line:1	file:
	Y	Units/c-define-mixed.d/input.c	6;"	d	line:6	file:

New output with this patch:

	$ ./ctags -o - --excmd=mixed --fields=+n Units/c-define-mixed.d/input.c
	X	Units/c-define-mixed.d/input.c	/^#define X /;"	d	line:1	file:
	Y	Units/c-define-mixed.d/input.c	/^#define Y(/;"	d	line:6	file:

expected.tags files are also aligned to new corrected output.
New test case c-define-mixed.d is added.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>