clean up proc.c; use procsaved() to avoid tedious comments.

Reference: /n/atom/patch/applied/procclean
Date: Fri May 23 22:23:51 CES 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/nix/port/proc.c	Fri May 23 22:23:30 2014
+++ /sys/src/nix/port/proc.c	Fri May 23 22:23:30 2014
@@ -449,10 +449,7 @@
 		l = p;
 	}
 
-	/*
-	 *  p->mach == nil only when process state is saved
-	 */
-	if(p == nil || p->mach != nil){
+	if(p == nil || !procsaved(p)){
 		unlock(sch);
 		return nil;
 	}
@@ -642,7 +639,7 @@
 	start = perfticks();
 	sch = m->sch;
 	/* cooperative scheduling until the clock ticks */
-	if((p=m->readied) && p->mach==0 && p->state==Ready
+	if((p=m->readied) != nil && procsaved(p) && p->state==Ready
 	&& sch->runq[Nrq-1].head == nil && sch->runq[Nrq-2].head == nil
 	&& (p->wired == nil || p->wired->machno == m->machno)){
 		sch->skipscheds++;
@@ -714,8 +711,7 @@
 	pl = splhi();
 	sch = procsched(p);
 	lock(sch);
-	/* Only reliable way to see if we are Running */
-	if(p->mach == nil) {
+	if(procsaved(p)){
 		p->newtlb = 1;
 		ok = 1;
 	}
@@ -736,16 +732,16 @@
 
 	p->state = Scheding;
 	p->psstate = "New";
-	p->mach = 0;
-	p->qnext = 0;
+	p->mach = nil;
+	p->qnext = nil;
 	p->nchild = 0;
 	p->nwait = 0;
-	p->waitq = 0;
-	p->parent = 0;
-	p->pgrp = 0;
-	p->egrp = 0;
-	p->fgrp = 0;
-	p->rgrp = 0;
+	p->waitq = nil;
+	p->parent = nil;
+	p->pgrp = nil;
+	p->egrp = nil;
+	p->fgrp = nil;
+	p->rgrp = nil;
 	p->pdbg = 0;
 	p->kp = 0;
 	if(up != nil && up->procctl == Proc_tracesyscall)
@@ -755,7 +751,7 @@
 	p->syscalltrace = nil;
 	p->notepending = 0;
 	p->nnote = 0;
-	p->ureg = 0;
+	p->ureg = nil;
 	p->privatemem = 0;
 	p->noswap = 0;
 	p->errstr = p->errbuf0;
--- /sys/src/nix/port/portfns.h	Fri May 23 22:23:30 2014
+++ /sys/src/nix/port/portfns.h	Fri May 23 22:23:30 2014
@@ -252,6 +252,7 @@
 void		procpriority(Proc*, int, int);
 void		procrestore(Proc*);
 void		procsave(Proc*);
+#define		procsaved(p)	((p)->mach == nil)
 void		(*proctrace)(Proc*, int, vlong);
 void		proctracepid(Proc*);
 void		procwired(Proc*, int);