tests: use "Exit $fail", not (exit $fail); exit $fail

* tests/test-lib.sh (Exit): New function by Ralf Wildenhues in automake
http://git.sv.gnu.org/gitweb/?p=automake.git;a=commitdiff;h=20594c08f63
* tests/**: Convert all uses:

This restrictive change converted the vast majority:

  git grep -l '^(exit \$fail); exit \$fail$' \
    | xargs perl -pi -e 's/'^\(exit \$fail\); exit \$fail$/Exit \$fail/'

And this did the rest, plus a few undesirable ones, so I manually
backed out the changes to ChangeLog-* and build-aux/check.mk:

  git grep -l -E '\(exit [^)]+\); exit ' \
    | xargs perl -pi -e 's/\(exit (.+?)\); exit \1/Exit $1/'

tests/ln/backup-1

@@ -31,4 +31,4 @@ touch a b || framework_failure
 ln b b~ || fail=1
 ln -f --b=simple a b || fail=1
 
-(exit $fail); exit $fail
+Exit $fail

tests/ln/hard-backup

@@ -34,4 +34,4 @@ EOF
 
 compare out exp || fail=1
 
-(exit $fail); exit $fail
+Exit $fail

tests/ln/misc

@@ -149,4 +149,4 @@ ln foo '' 2> /dev/null
 
 # ===================================================
 
-(exit $fail); exit $fail
+Exit $fail

tests/ln/sf-1

@@ -34,4 +34,4 @@ case `cat err` in
   *) fail=1 ;;
 esac
 
-(exit $fail); exit $fail
+Exit $fail

tests/ln/target-1

@@ -32,4 +32,4 @@ mkdir d || framework_failure
 fail=0
 ln -s --target-dir=d ../f || fail=1
 
-(exit $fail); exit $fail
+Exit $fail