xdemineur build fails

[Paul Goyette <paul%whooppee.com@localhost>]

...
--- main.o ---
main.c: In function 'main':
main.c:49:12: error: implicit declaration of function 'strcmp' [-Wimplicit-function-declaration]
   49 |       if ( strcmp ( argv[i] , "-v" ) == 0 )
      |            ^~~~~~
main.c:27:1: note: include '<string.h>' or provide a declaration of 'strcmp'
   26 | #include "xdemineur.h"
  +++ |+#include <string.h>
   27 |
*** [main.o] Error code 1
...

+---------------------+--------------------------+----------------------+
| Paul Goyette (.sig) | PGP Key fingerprint:     | E-mail addresses:    |
| (Retired)           | 1B11 1849 721C 56C8 F63A | paul%whooppee.com@localhost    |
| Software Developer  | 6E2E 05FD 15CE 9F2D 5102 | pgoyette%netbsd.org@localhost  |
| & Network Engineer  |                          | pgoyette99%gmail.com@localhost |
+---------------------+--------------------------+----------------------+