REORG: errors: split errors reporting function from log.c

Move functions related to errors output on stderr from log.c to a newly
created errors.c file. It targets print_message and
ha_alert/warning/notice/diag functions and related startup_logs feature.
diff --git a/Makefile b/Makefile
index 6571dc6..5344df5 100644
--- a/Makefile
+++ b/Makefile
@@ -896,7 +896,7 @@
         src/hpack-tbl.o src/ebimtree.o src/auth.o src/ebsttree.o               \
         src/ebistree.o src/base64.o src/wdt.o src/pipe.o src/http_acl.o        \
         src/hpack-enc.o src/dict.o src/dgram.o src/init.o src/hpack-huff.o     \
-        src/freq_ctr.o src/ebtree.o src/hash.o src/version.o
+        src/freq_ctr.o src/ebtree.o src/hash.o src/version.o src/errors.o
 
 ifneq ($(TRACE),)
 OBJS += src/calltrace.o