Added missing 'restrict' to some kernels' cntx_t*.

Details:
- Added missing 'restrict' keyword to cntx_t* argument of function
  signatures corresponding to level-1v, level-1f, and level-1m kernels.
  This affected bli_l1v_ker_prot.h, bli_l1f_ker_prot.h, and
  bli_l1m_ker_prot.h. (The 'restrict' was already being used to
  qualify cntx_t* arguments for kernels defined in bli_l3_ker_prot.h.)
- Added comments to bli_l1v_ker.h, bli_l1f_ker.h, bli_l1m_ker.h, and
  bli_l3_ukr.h that help explain how those headers function to produce
  kernel prototypes using the prototype macros defined in the files
  mentioned above.

kernels/bgq/1/bli_axpyv_bgq_int.c

@@ -41,7 +41,7 @@ void bli_daxpyv_bgq_int
        double* restrict alpha,
        double* restrict x, inc_t incx,
        double* restrict y, inc_t incy,
-       cntx_t*          cntx
+       cntx_t* restrict cntx
      )
 {
 	if ( bli_zero_dim1( n ) ) return;

kernels/bgq/1/bli_dotv_bgq_int.c

@@ -42,7 +42,7 @@ void bli_ddotv_bgq_int
        double* restrict x, inc_t incx,
        double* restrict y, inc_t incy,
        double* restrict rho,
-       cntx_t*          cntx
+       cntx_t* restrict cntx
      )
 { 
 	bool_t use_ref = FALSE;