refactor(solutions): headers file in C

challenges/caesar-cipher/solutions/c/function/character.h

@@ -1,5 +1,5 @@
-#ifndef CHARACTER_H
-#define CHARACTER_H
+#ifndef __CHARACTER__
+#define __CHARACTER__
 
 /**
  * @brief Append a character to a string, assuming string points to an array

challenges/caesar-cipher/solutions/c/function/input.h

@@ -1,5 +1,5 @@
-#ifndef INPUT_H
-#define INPUT_H
+#ifndef __INPUT__
+#define __INPUT__
 
 /**
  * @brief Read a line from stdin.

challenges/caesar-cipher/solutions/c/function/string.h

@@ -1,5 +1,5 @@
-#ifndef STRING_H
-#define STRING_H
+#ifndef __STRING__
+#define __STRING__
 
 #define ALPHABET "ABCDEFGHIJKLMNOPQRSTUVWXYZ"