Remove source file that was only used for testing

kbhit.c

@@ -1,19 +0,0 @@
-/*
- * Keyboard test program.
- */
-
-#include <conio.h>
-
-int main(void)
-{
-    unsigned char c;
-
-    clrscr();
-    cputs("   Keyboard Test\r\n");
-
-    while (1) {
-        c = cgetc();
-        cputc(c);
-    }
-    return 0;
-}