patch 9.0.0057: has('patch-xxx') returns true

Problem:    has('patch-xxx') returns true.
Solution:   Check for digit. (closes #10751)

src/evalfunc.c

@@ -6473,7 +6473,7 @@ f_has(typval_T *argvars, typval_T *rettv)
 			     || (minor == VIM_VERSION_MINOR
 				 && has_patch(atoi((char *)name + 10))))));
 	    }
-	    else
+	    else if (isdigit(name[5]))
 		n = has_patch(atoi((char *)name + 5));
 	}
 	else if (STRICMP(name, "vim_starting") == 0)

src/testdir/test_expr.vim

@@ -41,6 +41,7 @@ func Test_version()
   call assert_false(has('patch-7.4.'))
   call assert_false(has('patch-9.1.0'))
   call assert_false(has('patch-9.9.1'))
+  call assert_false(has('patch-abc'))
 endfunc
 
 func Test_op_ternary()

src/version.c

@@ -735,6 +735,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    57,
 /**/
     56,
 /**/