Remove DLSYM_NEEDS_UNDERSCORE

Some non-ELF platforms in the past (BSD-based systems - OpenBSD, NetBSD,
FreeBSD and Mac OS X ~10.3) required dlsym() to have symbol names
prefixed with an underscore (_) character. This isn't relevant anymore
on current systems.

Author: petk

UPGRADING.INTERNALS

@@ -99,6 +99,8 @@ PHP 8.6 INTERNALS UPGRADE NOTES
     . --with-pic is now --enable-pic. The old flag will result in an error.
   . Symbol HAVE_ST_BLOCKS has been removed from php_config.h (use
     HAVE_STRUCT_STAT_ST_BLOCKS).
+  . Symbol DLSYM_NEEDS_UNDERSCORE for using dlsym() with an underscore prefix
+    in symbol names has been removed (obsolete on current systems).
 
 - Windows build system changes:
   . Function SETUP_OPENSSL() doesn't accept 6th argument anymore and doesn't

Zend/Zend.m4

@@ -111,20 +111,6 @@ AS_VAR_IF([php_cv_have_fpu_inline_asm_x86], [yes],
     [Define to 1 if FPU control word can be manipulated by inline assembler.])])
 ])
 
-dnl
-dnl ZEND_DLSYM_CHECK
-dnl
-dnl Ugly hack to check if dlsym() requires a leading underscore in symbol name.
-dnl
-AC_DEFUN([ZEND_DLSYM_CHECK], [dnl
-AC_MSG_CHECKING([whether dlsym() requires a leading underscore in symbol names])
-_LT_TRY_DLOPEN_SELF([AC_MSG_RESULT([no])], [
-  AC_MSG_RESULT([yes])
-  AC_DEFINE([DLSYM_NEEDS_UNDERSCORE], [1],
-    [Define to 1 if 'dlsym()' requires a leading underscore in symbol names.])
-], [AC_MSG_RESULT([no])], [])
-])
-
 dnl
 dnl ZEND_INIT
 dnl
@@ -168,7 +154,6 @@ AC_CHECK_FUNC([sigsetjmp],,
 
 ZEND_CHECK_STACK_DIRECTION
 ZEND_CHECK_FLOAT_PRECISION
-ZEND_DLSYM_CHECK
 ZEND_CHECK_GLOBAL_REGISTER_VARIABLES
 ZEND_CHECK_PRESERVE_NONE
 ZEND_CHECK_CPUID_COUNT

Zend/zend_portability.h

@@ -194,11 +194,7 @@
 #  define DL_LOAD(libname)			dlopen(libname, PHP_RTLD_MODE | RTLD_GLOBAL)
 # endif
 # define DL_UNLOAD					dlclose
-# if defined(DLSYM_NEEDS_UNDERSCORE)
-#  define DL_FETCH_SYMBOL(h,s)		dlsym((h), "_" s)
-# else
-#  define DL_FETCH_SYMBOL			dlsym
-# endif
+# define DL_FETCH_SYMBOL			dlsym
 # define DL_ERROR					dlerror
 # define DL_HANDLE					void *
 # define ZEND_EXTENSIONS_SUPPORT	1