Remove some presumably unnecessary leftovers from ancient times

I could not find that SHORTSTDC3 or SHORTSTDCPP3 would have any
meaning. They only occur here (and in our history).

Change-Id: I45141e60c144207fbf3fc0c5e59340b80951b212

solenv/gbuild/platform/com_GCC_defs.mk

@@ -39,9 +39,6 @@ ifeq ($(strip $(gb_COMPILEROPTFLAGS)),)
 gb_COMPILEROPTFLAGS := -O2
 endif
 
-gb_SHORTSTDC3 := 1
-gb_SHORTSTDCPP3 := 6
-
 gb_CPPU_ENV := gcc3
 
 gb_AFLAGS := $(AFLAGS)

solenv/gbuild/platform/solaris.mk

@@ -315,8 +315,6 @@ $(call gb_InstallModuleTarget_add_defs,$(1),\
 	$(gb_CPUDEFS) \
 	$(gb_OSDEFS) \
 	-DCOMID=gcc3 \
-	-DSHORTSTDC3=$(gb_SHORTSTDC3) \
-	-DSHORTSTDCPP3=$(gb_SHORTSTDCPP3) \
 	-D_gcc3 \
 )
 

solenv/gbuild/platform/unxgcc.mk

@@ -314,8 +314,6 @@ $(call gb_InstallModuleTarget_add_defs,$(1),\
 	$(gb_CPUDEFS) \
 	$(gb_OSDEFS) \
 	-DCOMID=gcc3 \
-	-DSHORTSTDC3=$(gb_SHORTSTDC3) \
-	-DSHORTSTDCPP3=$(gb_SHORTSTDCPP3) \
 	-D_gcc3 \
 )