libgo: don't unset in shell script

Reportedly ksh fails to unset a variable that was not previously set.
    Change match.sh and gotest to not unset LANG, but instead set LANG=C.
    Also don't combine exporting and setting variable in a single statement.
    
    Reviewed-on: https://go-review.googlesource.com/26999

From-SVN: r239443

gcc/go/gofrontend/MERGE

@@ -1,4 +1,4 @@
-d51890dc96a2a33484623728bdc8ac258645e9cc
+24e0c4c98e0614b1892316aca787f1c564f2d269
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/match.sh

@@ -10,10 +10,10 @@
 
 set -e
 
-unset LANG
+LANG=C
 LC_ALL=C
 LC_CTYPE=C
-export LC_ALL LC_CTYPE
+export LANG LC_ALL LC_CTYPE
 
 srcdir=""
 goarch=""

libgo/testsuite/gotest

@@ -10,9 +10,10 @@
 
 # Makes egrep,grep work better in general if we put them
 # in ordinary C mode instead of what the current language is.
-unset LANG
-export LC_ALL=C
-export LC_CTYPE=C
+LANG=C
+LC_ALL=C
+LC_CTYPE=C
+export LANG LC_ALL LC_CTYPE
 
 GC=${GC:-gccgo}
 GL=${GL:-${GC-gccgo}}