Remove trailing whitespace

Additionally, added a GitHub Action to ensure no more trailing
whitespace will creep in again in the future.

I'm excluding Markdown files from this check, since trailing whitespace
is significant there, and also excluding `build-aux/install-sh` because
there is significant trailing whitespace on the line that sets
`defaultIFS`.

test/include/test/SFMT-params.h

@@ -45,7 +45,7 @@
 /*-----------------
   BASIC DEFINITIONS
   -----------------*/
-/** Mersenne Exponent. The period of the sequence 
+/** Mersenne Exponent. The period of the sequence
  *  is a multiple of 2^MEXP-1.
  * #define MEXP 19937 */
 /** SFMT generator has an internal state array of 128-bit integers,
@@ -63,25 +63,25 @@
   following definitions are in paramsXXXX.h file.
   ----------------------*/
 /** the pick up position of the array.
-#define POS1 122 
+#define POS1 122
 */
 
 /** the parameter of shift left as four 32-bit registers.
 #define SL1 18
  */
 
-/** the parameter of shift left as one 128-bit register. 
- * The 128-bit integer is shifted by (SL2 * 8) bits. 
-#define SL2 1 
+/** the parameter of shift left as one 128-bit register.
+ * The 128-bit integer is shifted by (SL2 * 8) bits.
+#define SL2 1
 */
 
 /** the parameter of shift right as four 32-bit registers.
 #define SR1 11
 */
 
-/** the parameter of shift right as one 128-bit register. 
- * The 128-bit integer is shifted by (SL2 * 8) bits. 
-#define SR2 1 
+/** the parameter of shift right as one 128-bit register.
+ * The 128-bit integer is shifted by (SL2 * 8) bits.
+#define SR2 1
 */
 
 /** A bitmask, used in the recursion.  These parameters are introduced
@@ -89,7 +89,7 @@
 #define MSK1 0xdfffffefU
 #define MSK2 0xddfecb7fU
 #define MSK3 0xbffaffffU
-#define MSK4 0xbffffff6U 
+#define MSK4 0xbffffff6U
 */
 
 /** These definitions are part of a 128-bit period certification vector.