qapi, qemu-options: make all parsing visitors parse boolean options the same

OptsVisitor, StringInputVisitor and the keyval visitor have
three different ideas of how a human could write the value of
a boolean option.  Pay homage to the backwards-compatibility
gods and make the new common helper accept all four sets (on/off,
true/false, y/n and yes/no), but remove case-insensitivity.

Since OptsVisitor is supposed to match qemu-options, adjust
it as well.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20201103161339.447118-1-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/qapi/qapi-util.c b/qapi/qapi-util.c
index 29a6c98..3c24bb3 100644
--- a/qapi/qapi-util.c
+++ b/qapi/qapi-util.c
@@ -13,6 +13,7 @@
 #include "qemu/osdep.h"
 #include "qapi/error.h"
 #include "qemu/ctype.h"
+#include "qapi/qmp/qerror.h"
 
 const char *qapi_enum_lookup(const QEnumLookup *lookup, int val)
 {
@@ -40,6 +41,28 @@
     return def;
 }
 
+bool qapi_bool_parse(const char *name, const char *value, bool *obj, Error **errp)
+{
+    if (g_str_equal(value, "on") ||
+        g_str_equal(value, "yes") ||
+        g_str_equal(value, "true") ||
+        g_str_equal(value, "y")) {
+        *obj = true;
+        return true;
+    }
+    if (g_str_equal(value, "off") ||
+        g_str_equal(value, "no") ||
+        g_str_equal(value, "false") ||
+        g_str_equal(value, "n")) {
+        *obj = false;
+        return true;
+    }
+
+    error_setg(errp, QERR_INVALID_PARAMETER_VALUE, name,
+               "'on' or 'off'");
+    return false;
+}
+
 /*
  * Parse a valid QAPI name from @str.
  * A valid name consists of letters, digits, hyphen and underscore.