Linux: update gathering information regarding threads

Document for each block gathering information about a task whether the
information is shared for the whole process or specific to a single
userland thread.

Also avoid system calls for process-shared information and reuse the
information from the main task.

Scheduling.c

@@ -156,6 +156,9 @@ const char* Scheduling_formatPolicy(int policy) {
    }
 }
 
+/*
+ * Gather scheduling policy (thread-specific data)
+ */
 void Scheduling_readProcessPolicy(Process* proc) {
    proc->scheduling_policy = sched_getscheduler(Process_getPid(proc));
 }

linux/LibNl.c

@@ -193,6 +193,9 @@ static int handleNetlinkMsg(struct nl_msg* nlmsg, void* linuxProcess) {
    return NL_OK;
 }
 
+/*
+ * Gather delay-accounting information (thread-specific data)
+ */
 void LibNl_readDelayAcctData(LinuxProcessTable* this, LinuxProcess* process) {
    struct nl_msg* msg;
 

linux/LinuxProcess.c

@@ -154,6 +154,9 @@ static int LinuxProcess_effectiveIOPriority(const LinuxProcess* this) {
 #define SYS_ioprio_set __NR_ioprio_set
 #endif
 
+/*
+ * Gather I/O scheduling class and priority (thread-specific data)
+ */
 IOPriority LinuxProcess_updateIOPriority(Process* p) {
    IOPriority ioprio = 0;
 // Other OSes masquerading as Linux (NetBSD?) don't have this syscall