implement fmtmsg function

contributed by Isaac Dunham. this seems to be the last interface that
was missing for complete POSIX 2008 base + XSI coverage.

include/fmtmsg.h

@@ -0,0 +1,47 @@
+#ifndef _FMTMSG_H
+#define _FMTMSG_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define MM_HARD		1
+#define MM_SOFT		2
+#define MM_FIRM		4
+
+#define MM_APPL		8
+#define MM_UTIL		16
+#define MM_OPSYS	32
+
+#define MM_RECOVER	64
+#define MM_NRECOV	128
+
+#define MM_PRINT	256
+#define MM_CONSOLE	512
+
+#define MM_NULLMC	0L
+
+#define MM_HALT		1
+#define MM_ERROR	2
+#define MM_WARNING	3
+#define MM_INFO		4
+#define MM_NOSEV	0
+
+#define MM_OK		0
+#define MM_NOTOK	(-1)
+#define MM_NOMSG	1
+#define MM_NOCON	4
+
+#define MM_NULLLBL	((char*)0)
+#define MM_NULLTXT	((char*)0)
+#define MM_NULLACT	((char*)0)
+#define MM_NULLTAG	((char*)0)
+#define MM_NULLSEV	0
+
+int fmtmsg(long, const char *, int, const char *, const char *, const char *);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif