php requires bison and flex

apache/apache.spec

@@ -151,7 +151,7 @@ BuildPreReq:  perl
 PreReq:       perl
 %endif
 %if "%{mod_php}" == "yes"
-BuildPreReq:  make
+BuildPreReq:  make, bison, flex
 %if "%{php_mysql}" == "yes"
 BuildPreReq:  mysql
 %endif