dtc: fix some more -Wshadow warnings

Building on a RHEL6 system produced the following -Wshadow warnings in
fstree.c, util.c and checks.c:

cc1: warnings being treated as errors
checks.c: In function 'parse_checks_option':
checks.c:709: error: declaration of 'optarg' shadows a global
declaration
/usr/include/getopt.h:59: error: shadowed declaration is here
make[1]: *** [checks.o] Error 1
make[1]: *** Waiting for unfinished jobs....
make[1]: *** Waiting for unfinished jobs....
cc1: warnings being treated as errors
fstree.c: In function 'read_fstree':
fstree.c:40: error: declaration of 'tmpnam' shadows a global
declaration
/usr/include/stdio.h:208: error: shadowed declaration is here
make[1]: *** [fstree.o] Error 1
cc1: warnings being treated as errors
util.c: In function 'xstrdup':
util.c:42: error: declaration of 'dup' shadows a global declaration
/usr/include/unistd.h:528: error: shadowed declaration is here

Fix all of these -Wshadow warnings by using slightly different variable
names which won't collide with anything else.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
4 files changed