use strcasestr from glibc, instead of redefining it.

Index: uci2wb-4.1+git200714/UCI2WB.c
===================================================================
--- uci2wb-4.1+git200714.orig/UCI2WB.c
+++ uci2wb-4.1+git200714/UCI2WB.c
@@ -60,8 +60,6 @@ int unit = 1, drawOffer, scores[99], mpv
 
 FILE *toE, *fromE, *fromF;
 
-char *strcasestr (char *p, char *q) { while(*p) { char *r=p++, *s=q; while(tolower(*r++) == tolower(*s) && *s) s++; if(!*s) return p-1; } return NULL; }
-
 #ifdef WIN32
 WinPipe(HANDLE *hRd, HANDLE *hWr)
 {