compat: remove strnlen back-compat code

This was needed for mingw (not mingw-w64), and some older versions of
macOS, which we no-longer support.

Author: fanquake

build_msvc/bitcoin_config.h.in

@@ -125,10 +125,6 @@
    don't. */
 #define HAVE_DECL_STRERROR_R 0
 
-/* Define to 1 if you have the declaration of `strnlen', and to 0 if you
-   don't. */
-#define HAVE_DECL_STRNLEN 1
-
 /* Define if the dllexport attribute is supported. */
 #define HAVE_DLLEXPORT_ATTRIBUTE 1
 

configure.ac

@@ -984,7 +984,6 @@ AC_CHECK_DECLS([getifaddrs, freeifaddrs],[CHECK_SOCKET],,
     [#include <sys/types.h>
     #include <ifaddrs.h>]
 )
-AC_CHECK_DECLS([strnlen])
 
 dnl These are used for daemonization in bitcoind
 AC_CHECK_DECLS([fork])

src/Makefile.am

@@ -606,7 +606,6 @@ libbitcoin_util_a_SOURCES = \
   chainparamsbase.cpp \
   clientversion.cpp \
   compat/glibcxx_sanity.cpp \
-  compat/strnlen.cpp \
   fs.cpp \
   interfaces/echo.cpp \
   interfaces/handler.cpp \

src/compat.h

@@ -80,10 +80,6 @@ typedef int32_t ssize_t;
 #endif
 #endif
 
-#if HAVE_DECL_STRNLEN == 0
-size_t strnlen( const char *start, size_t max_len);
-#endif // HAVE_DECL_STRNLEN
-
 #ifndef WIN32
 typedef void* sockopt_arg_type;
 #else