logd: initial checkin.

* Create a new userspace log daemon for handling logging messages.

Original-Change-Id: I75267df16359684490121e6c31cca48614d79856
Signed-off-by: Nick Kralevich <nnk@google.com>

* Merge conflicts
* rename new syslog daemon to logd to prevent confusion with bionic syslog
* replace racy getGroups call with KISS call to client->getGid()
* Timestamps are filed at logging source
* insert entries into list in timestamp order
* Added LogTimeEntry tail filtration handling
* Added region locking around LogWriter list
* separate threads for each writer
* /dev/socket/logd* permissions

Signed-off-by: Mark Salyzyn <salyzyn@google.com>

(cherry picked from commit 3e76e0a49760c4970b7cda6153e51026af98e4f3)

Author: Nick Kralevich <nnk@google.com>
Change-Id: Ice88b1412d8f9daa7f9119b2b5aaf684a5e28098
diff --git a/include/private/android_filesystem_config.h b/include/private/android_filesystem_config.h
index 0ed0d78..9c26baf 100644
--- a/include/private/android_filesystem_config.h
+++ b/include/private/android_filesystem_config.h
@@ -76,6 +76,7 @@
 #define AID_SDCARD_PICS   1033  /* external storage photos access */
 #define AID_SDCARD_AV     1034  /* external storage audio/video access */
 #define AID_SDCARD_ALL    1035  /* access all users external storage */
+#define AID_LOGD          1036  /* log daemon */
 
 #define AID_SHELL         2000  /* adb and debug shell user */
 #define AID_CACHE         2001  /* cache access */
@@ -151,6 +152,7 @@
     { "sdcard_pics",   AID_SDCARD_PICS, },
     { "sdcard_av",     AID_SDCARD_AV, },
     { "sdcard_all",    AID_SDCARD_ALL, },
+    { "logd",          AID_LOGD, },
 
     { "shell",         AID_SHELL, },
     { "cache",         AID_CACHE, },