Silence funny warning in 2019/adamovsky

The funny warning is:

prog.c:19:515: warning: line splicing in Doxygen comments are not supported [-Wdocumentation]
   19 | void X(char*f,int r){ fputs(f,stderr);exit(r);}typedef w{w* (*t) (w*x);w* (*l) (w*x,w*y);w*a;long long p;}A;h(R) {x[N-1].p++;e x;}h(Ch) ;h(Y) ;h(fA) ;d(fD) ;d(fT) ;d(fW) ;d(fCh) ;d(rA2) ;d(fA2) ;d(rY2) ;d(Y2) ;d(rS2) ;d(fS22) ;d(rD) ;d(rE) ;d(rT) ;d(rC) ;void D(A*f) {if(f&&!--f[N-1].p) {if(u(f)!=fW&&u(f)!=fCh) D(f[1].a);if(u(f)!=fT) D(f[2].a);if(u(f)!=rE&&u(f)!=rT&&u(f)!=rC) D(f[3].a);free(f);}}int ch=EOF,c;FILE*p;A T[256][2];void U(void) {do{if(c==EOF) e;if(T[c][0].t) e;if(!T[c][1].p) E;if(T[c][1].p==4) for(/**??/
      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   ^
1 warning generated.

.. obviously confused by trigraphs.

2019/adamovsky/Makefile

@@ -38,7 +38,7 @@ include ../../var.mk
 
 # Common C compiler warnings to silence
 #
-CSILENCE= -Wno-trigraphs -Wno-comment -Wno-misleading-indentation
+CSILENCE= -Wno-trigraphs -Wno-comment -Wno-misleading-indentation -Wno-documentation
 
 # Attempt to silence unknown warnings
 #