Remove HAVE_STDARG_H

The C89 standard and later defines the `<stdarg.h>` header as part of
the standard headers [1]. On current systems it is always present and
can be included unconditionally.

Checking for presence and functionality of the `<stdarg.h>` header and
variadic function is not relevant anymore on current systems since this
is always available.

Also Autoconf suggests relying on at least C89 or above [2] and [3].

The following files were regenerated with re2c 1.0.3:
- Zend/zend_language_scanner.c
- Zend/zend_language_scanner_defs.h

Refs:
[1] https://port70.net/~nsz/c/c89/c89-draft.html#4.1.2
[2] http://git.savannah.gnu.org/cgit/autoconf.git/tree/lib/autoconf/headers.m4
[3] https://www.gnu.org/software/autoconf/manual/autoconf-2.69/autoconf.html

Author: petk

TSRM/TSRM.c

@@ -15,10 +15,7 @@
 #ifdef ZTS
 
 #include <stdio.h>
-
-#if HAVE_STDARG_H
 #include <stdarg.h>
-#endif
 
 typedef struct _tsrm_tls_entry tsrm_tls_entry;
 

TSRM/tsrm.m4

@@ -7,8 +7,6 @@ dnl AC_REQUIRE([AM_PROG_CC_STDC])dnl
 AC_REQUIRE([AC_PROG_CC_C_O])dnl
 AC_REQUIRE([AC_PROG_RANLIB])dnl
 
-AC_CHECK_HEADERS(stdarg.h)
-
 AC_CHECK_FUNCS(sigprocmask)
 
 AX_FUNC_WHICH_GETHOSTBYNAME_R()

Zend/Zend.m4

@@ -51,7 +51,6 @@ stdint.h \
 limits.h \
 malloc.h \
 unistd.h \
-stdarg.h \
 sys/types.h \
 sys/time.h \
 signal.h \

Zend/zend_API.c

@@ -30,9 +30,7 @@
 #include "zend_closures.h"
 #include "zend_inheritance.h"
 
-#ifdef HAVE_STDARG_H
 #include <stdarg.h>
-#endif
 
 /* these variables are true statics/globals, and have to be mutex'ed on every access */
 ZEND_API HashTable module_registry;

Zend/zend_compile.h

@@ -23,9 +23,7 @@
 #include "zend.h"
 #include "zend_ast.h"
 
-#ifdef HAVE_STDARG_H
-# include <stdarg.h>
-#endif
+#include <stdarg.h>
 
 #include "zend_llist.h"