Fix configure failure in configure due to undefined `exit`

Index: maintain_squidguard-upstream-1.6.0/configure.ac
===================================================================
--- maintain_squidguard-upstream-1.6.0.orig/configure.ac
+++ maintain_squidguard-upstream-1.6.0/configure.ac
@@ -237,7 +237,7 @@ if test "$with_ldap" = "yes"; then
         {
            LDAP *p;
            p = ldap_init("localhost", LDAP_PORT);
-           exit(0);
+           return 0;
         }
         ]])],,[
            echo
@@ -271,7 +271,7 @@ if test "$with_mysql" != "no"; then
   fi
 
   AC_MSG_CHECKING(for mysql)
-  MYSQLLINE="                    | USERQUERY WORD WORD WORD WORD { sgSourceUserQuery(\$2,\$3,\$4,\$5); }"
+  MYSQLLINE="                    | USERQUERY WORD { sgSourceUserQuery(\$2); }"
 
   for i in $mysql_directory; do
     if test -r $i/include/mysql/mysql.h; then
@@ -355,8 +355,8 @@ AC_RUN_IFELSE([AC_LANG_SOURCE([[
 #endif
         ver = major + ((float) minor / 1000);
         if (ver >= 2.006)
-			exit (0);
-		exit (1);
+			return 0;
+		return 1;
 	}	
 	]])],
 	[db_ok_version=yes],
@@ -390,8 +390,8 @@ AC_RUN_IFELSE([AC_LANG_SOURCE([[
 #endif
         ver = major + ((float) minor / 1000);
         if (ver > 2.007 && ver < 3.002)
-			exit (1);
-		exit (0);
+			return 1;
+		return 0;
 	}	
 	]])],
 	[db_ok_version=yes],
@@ -426,8 +426,8 @@ AC_RUN_IFELSE([AC_LANG_SOURCE([[
 #endif
         ver = major + ((float) minor / 1000);
         if (ver >= 3.002)
-			exit (0);
-		exit (1);
+			return 0;
+		return 1;
 	}	
 	]])],
 	[dbg2_ok_version=yes],
@@ -454,8 +454,8 @@ AC_RUN_IFELSE([AC_LANG_SOURCE([[
 #endif
         ver = major + ((float) minor / 1000);
         if (ver >= 4.002)
-			exit (0);
-		exit (1);
+			return 0;
+		return 1;
 	}	
 	]])],
 	[dbg3_ok_version=yes],