Bug 1416020 - Remove unused variables from client.mk; r=nalexander

The last use of PERL was removed recently.

The last use of comma was removed by c8276e89a513 in 2008.

The last use of SH was... never AFAICT. The variable was
defined but unused in the initial import of client.mk from CVS
in 1998.

MozReview-Commit-ID: LFqcVRf36wf

client.mk

@@ -16,8 +16,6 @@
 #######################################################################
 # Defines
 
-comma := ,
-
 ifdef MACH
 ifndef NO_BUILDSTATUS_MESSAGES
 define BUILDSTATUS
@@ -42,8 +40,6 @@ TOPSRCDIR := $(CWD)
 endif
 endif
 
-SH := /bin/sh
-PERL ?= perl
 PYTHON ?= $(shell which python2.7 > /dev/null 2>&1 && echo python2.7 || echo python)
 
 CONFIG_GUESS := $(shell $(TOPSRCDIR)/build/autoconf/config.guess)