patch 8.2.0271: the "num64" feature is available everywhere

Problem:    The "num64" feature is available everywhere and building without
            it causes problems.
Solution:   Graduage the "num64" feature. (James McCoy, closes #5650)
diff --git a/src/message.c b/src/message.c
index 935fd8c..9ab0eae 100644
--- a/src/message.c
+++ b/src/message.c
@@ -4246,10 +4246,8 @@
 #  define TMP_LEN 350	// On my system 1e308 is the biggest number possible.
 			// That sounds reasonable to use as the maximum
 			// printable.
-# elif defined(FEAT_NUM64)
-#  define TMP_LEN 66
 # else
-#  define TMP_LEN 34
+#  define TMP_LEN 66
 # endif
 	    char    tmp[TMP_LEN];
 
@@ -4374,11 +4372,7 @@
 		if (length_modifier == 'l' && *p == 'l')
 		{
 		    // double l = long long
-# ifdef FEAT_NUM64
 		    length_modifier = 'L';
-# else
-		    length_modifier = 'l';	// treat it as a single 'l'
-# endif
 		    p++;
 		}
 	    }
@@ -4394,7 +4388,7 @@
 		default: break;
 	    }
 
-# if defined(FEAT_EVAL) && defined(FEAT_NUM64)
+# if defined(FEAT_EVAL)
 	    switch (fmt_spec)
 	    {
 		case 'd': case 'u': case 'o': case 'x': case 'X':
@@ -4516,11 +4510,9 @@
 		    long int long_arg = 0;
 		    unsigned long int ulong_arg = 0;
 
-# ifdef FEAT_NUM64
 		    // only defined for length modifier ll
 		    varnumber_T llong_arg = 0;
 		    uvarnumber_T ullong_arg = 0;
-# endif
 
 		    // only defined for b conversion
 		    uvarnumber_T bin_arg = 0;
@@ -4581,19 +4573,17 @@
 			    else if (long_arg < 0)
 				arg_sign = -1;
 			    break;
-# ifdef FEAT_NUM64
 			case 'L':
 			    llong_arg =
-#  if defined(FEAT_EVAL)
+# if defined(FEAT_EVAL)
 					tvs != NULL ? tv_nr(tvs, &arg_idx) :
-#  endif
+# endif
 					    va_arg(ap, varnumber_T);
 			    if (llong_arg > 0)
 				arg_sign =  1;
 			    else if (llong_arg < 0)
 				arg_sign = -1;
 			    break;
-# endif
 			}
 		    }
 		    else
@@ -4622,18 +4612,16 @@
 				if (ulong_arg != 0)
 				    arg_sign = 1;
 				break;
-# ifdef FEAT_NUM64
 			    case 'L':
 				ullong_arg =
-#  if defined(FEAT_EVAL)
+# if defined(FEAT_EVAL)
 					    tvs != NULL ? (uvarnumber_T)
 							tv_nr(tvs, &arg_idx) :
-#  endif
+# endif
 						va_arg(ap, uvarnumber_T);
 				if (ullong_arg != 0)
 				    arg_sign = 1;
 				break;
-# endif
 			}
 		    }
 
@@ -4687,17 +4675,13 @@
 			    ;
 			else if (length_modifier == 'L')
 			{
-# ifdef FEAT_NUM64
-#  ifdef MSWIN
+# ifdef MSWIN
 			    f[f_l++] = 'I';
 			    f[f_l++] = '6';
 			    f[f_l++] = '4';
-#  else
-			    f[f_l++] = 'l';
-			    f[f_l++] = 'l';
-#  endif
 # else
 			    f[f_l++] = 'l';
+			    f[f_l++] = 'l';
 # endif
 			}
 			else
@@ -4735,11 +4719,9 @@
 			    case 'l': str_arg_l += sprintf(
 						tmp + str_arg_l, f, long_arg);
 				      break;
-# ifdef FEAT_NUM64
 			    case 'L': str_arg_l += sprintf(
 					       tmp + str_arg_l, f, llong_arg);
 				      break;
-# endif
 			    }
 			}
 			else
@@ -4754,11 +4736,9 @@
 			    case 'l': str_arg_l += sprintf(
 					       tmp + str_arg_l, f, ulong_arg);
 				      break;
-# ifdef FEAT_NUM64
 			    case 'L': str_arg_l += sprintf(
 					      tmp + str_arg_l, f, ullong_arg);
 				      break;
-# endif
 			    }
 			}