Centralise all sprintf()/snprintf() calls in a compatibility wrapper pv_snprintf()

src/include/pv.h

@@ -9,6 +9,8 @@
 #ifndef _PV_H
 #define _PV_H 1
 
+#include <stdlib.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -53,6 +55,12 @@ extern unsigned long long pv_getnum_ull(const char *);
  */
 extern int pv_getnum_check(const char *, pv_numtype_t);
 
+/*
+ * Wrapper for sprintf(), with less safe fallbacks for systems without that
+ * function.
+ */
+extern int pv_snprintf(char *, size_t, const char *, ...);
+
 /*
  * Main PV functions.
  */