fix build with -fno-common

--- a/ezmlm-get.c	2021-05-24 12:07:05.245657000 +0200
+++ b/ezmlm-get.c	2021-05-24 12:07:11.477657000 +0200
@@ -125,7 +125,7 @@
 
 int act = AC_NONE;		/* Action we do */
 int flageditor = 0;		/* if we're invoked for within dir/editor */
-struct stat st;
+static struct stat st;
 
 int flaglocked = 0;		/* if directory is locked */
 int flagq = 0;			/* don't use 'quoted-printable' */
@@ -157,7 +157,7 @@
 substdio ssindex;
 char indexbuf[1024];
 
-int fdlock;
+static int fdlock;
 
 void lockup(void)
 /* lock unless locked */
--- a/idxthread.c	2021-05-24 12:06:55.169657000 +0200
+++ b/idxthread.c	2021-05-24 12:07:09.197657000 +0200
@@ -39,13 +39,13 @@
 
 static char strnum[FMT_ULONG];
 
-struct stat st;
+static struct stat st;
 			/* if no data, these may be the entire table, so */
 			/* need to be static */
 static subentry sdummy;
 static authentry adummy;
 
-int fdlock;
+static int fdlock;
 
 /* NOTE: These do NOT prevent double locking */
 static void lockup(void)