lib: escape usage of strerror_l() if it doesn't exist in libc

uClibc doesn't implement strerror_l() and thus libnl starting from
3.2.29 couldn't be compiled with it any longer.

To work-around that problem we'll just do a check on strerror_l()
availability during configuration and if it's not there just fall back
to locale-less strerror().

See-also: 6c2d111177e91184073c44f83d4a6182aaba06d7

http://lists.infradead.org/pipermail/libnl/2017-March/002301.html

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Thomas Haller <thaller@redhat.com>
diff --git a/configure.ac b/configure.ac
index 68b285e..2739b99 100644
--- a/configure.ac
+++ b/configure.ac
@@ -121,6 +121,8 @@
 
 AC_CONFIG_SUBDIRS([doc])
 
+AC_CHECK_FUNCS([strerror_l])
+
 AC_CONFIG_FILES([
 Makefile
 libnl-3.0.pc