getopt_long.c: initialize optarg and optreset to avoid symbol clashes.

this has been happening to me eg. with amiga clib2 like:
/opt/cross_amigaos4/ppc-amigaos/SDK/clib2/lib/libc.a(unistd_getopt.o)(.text+0x0): In function `getopt':
: multiple definition of `getopt'
getopt_long.o(.text+0xc1c):/work/xmp-cli/src/getopt_long.c:481: first defined here
/opt/cross_amigaos4/lib/gcc/ppc-amigaos/4.2.4/../../../../ppc-amigaos/bin/ld: Warning: size of symbol `getopt' changed from 16 in getopt_long.o to 672 in /opt/cross_amigaos4/ppc-amigaos/SDK/clib2/lib/libc.a(unistd_getopt.o)
/opt/cross_amigaos4/ppc-amigaos/SDK/clib2/lib/libc.a(unistd_getopt.o)(.sdata+0x4): multiple definition of `optind'
getopt_long.o(.sdata+0x4):/work/xmp-cli/src/getopt_long.c:133: first defined here
/opt/cross_amigaos4/ppc-amigaos/SDK/clib2/lib/libc.a(unistd_getopt.o)(.sbss+0x0): multiple definition of `optopt'
getopt_long.o(.sdata+0x8):/work/xmp-cli/src/getopt_long.c:126: first defined here
/opt/cross_amigaos4/ppc-amigaos/SDK/clib2/lib/libc.a(unistd_getopt.o)(.sdata+0x0): multiple definition of `opterr'
getopt_long.o(.sdata+0x0):/work/xmp-cli/src/getopt_long.c:126: first defined here

src/getopt_long.c

@@ -60,8 +60,9 @@
 int	opterr = 1;		/* if error message should be printed */
 int	optind = 1;		/* index into parent argv vector */
 int	optopt = '?';		/* character checked for validity */
-int	optreset;		/* reset getopt */
-char    *optarg;		/* argument associated with option */
+/* initialize these two too to avoid symbol clashes from system libc: */
+int	optreset = 0;		/* reset getopt */
+char   *optarg = NULL;		/* argument associated with option */
 
 #define PRINT_ERROR	((opterr) && (*options != ':'))