(jm_AC_PREREQ_XSTRTOUMAX): Check for strtol and strtoimax,

as those declarations are made even in the unsigned case.

m4/xstrtoumax.m4

@@ -1,4 +1,4 @@
-#serial 3
+#serial 4
 
 # autoconf tests required for use of xstrtoumax.c
 
@@ -8,7 +8,7 @@ AC_DEFUN([jm_AC_PREREQ_XSTRTOUMAX],
   AC_REQUIRE([jm_AC_TYPE_UINTMAX_T])
   AC_REQUIRE([jm_AC_TYPE_LONG_LONG])
   AC_REQUIRE([jm_AC_TYPE_UNSIGNED_LONG_LONG])
-  AC_CHECK_DECLS([strtoul, strtoull, strtoumax])
+  AC_CHECK_DECLS([strtol, strtoul, strtoull, strtoimax, strtoumax])
   AC_CHECK_HEADERS(limits.h stdlib.h inttypes.h)
 
   AC_CACHE_CHECK([whether <inttypes.h> defines strtoumax as a macro],