biology/biosig: fix build with libc++ 19

With libc++ 19, biology/biosig fails to compile, with errors similar to:

  /usr/include/c++/v1/__math/special_functions.h:51:16: error: expected unqualified-id
     51 |   if (!__math::isfinite(__H_n)) {
        |                ^
  ./t230/../biosig-dev.h:932:22: note: expanded from macro 'isfinite'
    932 | # define isfinite(a) (-INFINITY < (a) && (a) < INFINITY)
        |                      ^

This is because biosig attempts to define its own isfinite() macro,
which it should not do. Stub out the incompatible definition.

PR:		281976
Approved by:	yuri (maintainer)
MFH:		2024Q4

(cherry picked from commit 08d6ba6fa1)

biology/biosig/files/patch-biosig4c++_biosig-dev.h

@@ -1,4 +1,4 @@
---- biosig4c++/biosig-dev.h.orig	2022-10-08 10:54:15 UTC
+--- biosig4c++/biosig-dev.h.orig	2024-08-03 10:06:47 UTC
 +++ biosig4c++/biosig-dev.h
 @@ -35,6 +35,8 @@
  #include <time.h>
@@ -9,16 +9,25 @@
  
  #ifdef __cplusplus
  extern "C" {
-@@ -549,6 +551,12 @@ HDRTYPE* sopen_extended(const char* FileName, const ch
- #elif defined(__linux__) 
+@@ -550,6 +552,12 @@ HDRTYPE* sopen_extended(const char* FileName, const ch
  #  include <endian.h>
  #  include <byteswap.h>
-+
+ 
 +#elif defined(__FreeBSD__) 
 +#  include <machine/endian.h>
 +#  define __BIG_ENDIAN _BIG_ENDIAN
 +#  define __LITTLE_ENDIAN _LITTLE_ENDIAN
 +#  define __BYTE_ORDER _BYTE_ORDER
- 
++
  #elif defined(__FreeBSD__)
  #  include <machine/endian.h>
+ 
+@@ -920,7 +928,7 @@ static inline void bef64a(  double i, void* r) {
+ #ifndef INFINITY
+ # define INFINITY (1.0/0.0)   /* positive infinity */
+ #endif
+-#ifndef isfinite
++#if 0
+ # define isfinite(a) (-INFINITY < (a) && (a) < INFINITY)
+ #endif
+