g: revert accidental change, document missing file type

rc/bin/g

@@ -14,7 +14,7 @@ case 0
          exit usage 
 case 1 
          pattern=$1 
-         files=(`{ls *.[bcChlmsy] *.ml[iyl] *.ml *.asm *.awk *.cc *.cgi *.cpp *.cs *.go *.goc *.java *.lx *.ms *.pl *.py *.rc *.tex *.xy >[2]/dev/null}) 
+         files=(`{ls *.[bcChlmsy] *.asm *.awk *.cc *.cgi *.cpp *.cs *.go *.goc *.java *.lx *.ms *.pl *.py *.rc *.tex *.xy >[2]/dev/null}) 
 case * 
          pattern=$1 
          shift 

sys/man/1/grep

@@ -117,7 +117,7 @@ are listed, it searches all files matching
 .B *.b *.c *.C *.h *.l *.m *.s *.y
 .B *.asm *.cc *.cs *.lx *.cgi *.pl
 .B *.py *.tex *.ms *.java *.xy *.go
-.B *.goc
+.B *.goc *.cpp
 .SH SOURCE
 .B /sys/src/cmd/grep
 .br