BUILD: bug: Fix error when compiling with -DDEBUG_STRICT_NOCRASH

BUILD: bug: Fix error when compiling with -DDEBUG_STRICT_NOCRASH

ha_backtrace_to_stderr() must be declared in CRASH_NOW() macro whe HAProxy
is compiled with DEBUG_STRICT_NOCRASH. Otherwise an error is reported during
compilation:

include/haproxy/bug.h:58:26: error: implicit declaration of function ‘ha_backtrace_to_stderr’ [-Werror=implicit-function-declaration]
   58 | #define CRASH_NOW() do { ha_backtrace_to_stderr(); } while (0)

This patch must be backported as far as 2.4.