Add unit test for tempfile()

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

tests/Makefile.am

@@ -4,10 +4,12 @@ CLEANFILES      = *~ *.trs *.log
 TESTS           =
 TESTS          += makepath
 TESTS          += pidfile
+TESTS          += tempfile
 TESTS          += tree
 
 check_PROGRAMS  = $(TESTS)
 
 # Ignore warnings about unused result, in e.g. write()
 CFLAGS          = -W -Wall -Wextra -Wno-unused-result
+CPPFLAGS        = -D_GNU_SOURCE
 LDADD           = -L../ ../libite.la