Replaced use of bool_t type with C99 bool.

Details:
- Textually replaced nearly all non-comment instances of bool_t with the
  C99 bool type. A few remaining instances, such as those in the files
  bli_herk_x_ker_var2.c, bli_trmm_xx_ker_var2.c, and
  bli_trsm_xx_ker_var2.c, were promoted to dim_t since they were being
  used not for boolean purposes but to index into an array.
- This commit constitutes the third phase of a transition toward using
  C99's bool instead of bool_t, which was raised in issue #420. The first
  phase, which cleaned up various typecasts in preparation for using
  bool as the basis for bool_t (instead of gint_t), was implemented by
  commit a69a4d7. The second phase, which redefined the bool_t typedef
  in terms of bool (from gint_t), was implemented by commit 2c554c2.

sandbox/ref99/blx_gemm_ref_var2.c

@@ -39,8 +39,8 @@
 
 typedef void (*FUNCPTR_T)
      (
-       bool_t           packa,
-       bool_t           packb,
+       bool             packa,
+       bool             packb,
        conj_t           conja,
        conj_t           conjb,
        dim_t            m,
@@ -79,8 +79,8 @@ void blx_gemm_ref_var2
 {
 	const num_t    dt        = bli_obj_dt( c );
 
-	const bool_t   packa     = bli_rntm_pack_a( rntm );
-	const bool_t   packb     = bli_rntm_pack_b( rntm );
+	const bool     packa     = bli_rntm_pack_a( rntm );
+	const bool     packb     = bli_rntm_pack_b( rntm );
 
 	const conj_t   conja     = bli_obj_conj_status( a );
 	const conj_t   conjb     = bli_obj_conj_status( b );
@@ -171,8 +171,8 @@ void blx_gemm_ref_var2
 \
 void PASTEMAC(ch,varname) \
      ( \
-       bool_t           packa, \
-       bool_t           packb, \
+       bool             packa, \
+       bool             packb, \
        conj_t           conja, \
        conj_t           conjb, \
        dim_t            m, \

sandbox/ref99/blx_gemm_ref_var2.h

@@ -51,8 +51,8 @@ void blx_gemm_ref_var2
 \
 void PASTEMAC(ch,varname) \
      ( \
-       bool_t           packa, \
-       bool_t           packb, \
+       bool             packa, \
+       bool             packb, \
        conj_t           conja, \
        conj_t           conjb, \
        dim_t            m, \