headers/os: Make headers generator-friendly

Make Haiku headers a bit more friendly to binding generators by:
- Giving some `enum`s names (especially those that appear in
default arguments).
- Converting an internal `inline` function into a macro so that
the result could be evaluated in compile time.

Change-Id: I770674ad8fa7b24ac30b6b447d52a4b4c2530b8a
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6716
Tested-by: Commit checker robot <[email protected]>
Reviewed-by: waddlesplash <[email protected]>

headers/os/app/AppDefs.h

@@ -25,7 +25,7 @@ extern const BCursor *B_CURSOR_I_BEAM;
 
 
 // System Message Codes
-enum {
+enum system_message_code {
 	B_ABOUT_REQUESTED			= '_ABR',
 	B_WINDOW_ACTIVATED			= '_ACT',
 	B_APP_ACTIVATED				= '_ACT',	// Same as B_WINDOW_ACTIVATED
@@ -93,7 +93,7 @@ enum {
 
 
 // Other Commands
-enum {
+enum command_code {
 	B_SET_PROPERTY				= 'PSET',
 	B_GET_PROPERTY				= 'PGET',
 	B_CREATE_PROPERTY			= 'PCRT',

headers/os/app/Roster.h

@@ -37,7 +37,7 @@ struct app_info {
 #define _B_APP_INFO_RESERVED1_	(0x10000000)
 
 // watching request flags
-enum {
+enum watching_request_flags {
 	B_REQUEST_LAUNCHED	= 0x00000001,
 	B_REQUEST_QUIT		= 0x00000002,
 	B_REQUEST_ACTIVATED	= 0x00000004,