sd-journal: make sure sd_journal_add_match() also accepts SIZE_MAX as size

In many of our internal functions that take a pointer + a size we have
introduced the rule that SIZE_MAX as size means: take strlen().

sd_journal_add_match() has something similar, but the special value is
0, not SIZE_MAX. This is a bit ugly, since a zero size data block is
theoretically fine. The only reason sd_journal_add_match() gets away
with using this special value is because valid matches must consist of
at least 2 chars, hence cannot be zero.

But let's make this more robust and less surprising when compared to the
rest of our code, and *also* accept SIZE_MAX to mean strlen().

No actual code changes, just some clean-up.

src/journal/bsod.c

@@ -75,12 +75,12 @@ static int acquire_first_emergency_log_message(char **ret) {
         if (r < 0)
                 return log_error_errno(r, "Failed to add boot ID filter: %m");
 
-        r = sd_journal_add_match(j, "_UID=0", 0);
+        r = sd_journal_add_match(j, "_UID=0", SIZE_MAX);
         if (r < 0)
                 return log_error_errno(r, "Failed to add User ID filter: %m");
 
         assert_cc(0 == LOG_EMERG);
-        r = sd_journal_add_match(j, "PRIORITY=0", 0);
+        r = sd_journal_add_match(j, "PRIORITY=0", SIZE_MAX);
         if (r < 0)
                 return log_error_errno(r, "Failed to add Emergency filter: %m");
 

src/journal/journalctl-filter.c

@@ -69,7 +69,7 @@ static int add_dmesg(sd_journal *j) {
         if (!arg_dmesg)
                 return 0;
 
-        r = sd_journal_add_match(j, "_TRANSPORT=kernel", 0);
+        r = sd_journal_add_match(j, "_TRANSPORT=kernel", SIZE_MAX);
         if (r < 0)
                 return r;
 
@@ -440,7 +440,7 @@ static int add_matches(sd_journal *j, char **args) {
                         have_term = true;
 
                 } else {
-                        r = sd_journal_add_match(j, *i, 0);
+                        r = sd_journal_add_match(j, *i, SIZE_MAX);
                         if (r < 0)
                                 return log_error_errno(r, "Failed to add match '%s': %m", *i);
                         have_term = true;