Add ABI compatability aliases.

GNU used several extensions that were incompatible with C99 and POSIX,
so they used alternate names for the standard functions.

The result is that we need these to run standards-conformant programs
that were linked with glibc.

src/misc/getopt.c

@@ -70,3 +70,5 @@ int getopt(int argc, char * const argv[], const char *optstring)
 	}
 	return c;
 }
+
+weak_alias(getopt, __posix_getopt);

src/stdio/fscanf.c

 #include <stdio.h>
 #include <stdarg.h>
+#include "libc.h"
 
 int fscanf(FILE *restrict f, const char *restrict fmt, ...)
 {
@@ -10,3 +11,5 @@ int fscanf(FILE *restrict f, const char *restrict fmt, ...)
 	va_end(ap);
 	return ret;
 }
+
+weak_alias(__isoc99_fscanf);

src/stdio/fwscanf.c

 #include <stdio.h>
 #include <stdarg.h>
 #include <wchar.h>
+#include "libc.h"
 
 int fwscanf(FILE *restrict f, const wchar_t *restrict fmt, ...)
 {
@@ -11,3 +12,5 @@ int fwscanf(FILE *restrict f, const wchar_t *restrict fmt, ...)
 	va_end(ap);
 	return ret;
 }
+
+weak_alias(fwscanf,__isoc99_fwscanf);

src/stdio/scanf.c

 #include <stdio.h>
 #include <stdarg.h>
+#include "libc.h"
 
 int scanf(const char *restrict fmt, ...)
 {
@@ -10,3 +11,5 @@ int scanf(const char *restrict fmt, ...)
 	va_end(ap);
 	return ret;
 }
+
+weak_alias(scanf,__isoc99_scanf);

src/stdio/sscanf.c

 #include <stdio.h>
 #include <stdarg.h>
+#include "libc.h"
 
 int sscanf(const char *restrict s, const char *restrict fmt, ...)
 {
@@ -10,3 +11,5 @@ int sscanf(const char *restrict s, const char *restrict fmt, ...)
 	va_end(ap);
 	return ret;
 }
+
+weak_alias(sscanf,__isoc99_sscanf);

src/stdio/swscanf.c

 #include <stdio.h>
 #include <stdarg.h>
 #include <wchar.h>
+#include "libc.h"
 
 int swscanf(const wchar_t *restrict s, const wchar_t *restrict fmt, ...)
 {
@@ -11,3 +12,5 @@ int swscanf(const wchar_t *restrict s, const wchar_t *restrict fmt, ...)
 	va_end(ap);
 	return ret;
 }
+
+weak_alias(swscanf,__isoc99_swscanf);

src/stdio/vfwscanf.c

@@ -14,6 +14,7 @@
 #include "shgetc.h"
 #include "intscan.h"
 #include "floatscan.h"
+#include "libc.h"
 
 #define SIZE_hh -2
 #define SIZE_h  -1
@@ -308,3 +309,5 @@ match_fail:
 	FUNLOCK(f);
 	return matches;
 }
+
+weak_alias(vfwscanf,__isoc99_vfwscanf);

src/stdio/vscanf.c

 #include <stdio.h>
 #include <stdarg.h>
+#include "libc.h"
 
 int vscanf(const char *restrict fmt, va_list ap)
 {
 	return vfscanf(stdin, fmt, ap);
 }
+
+weak_alias(vscanf,__isoc99_vscanf);

src/stdio/vsscanf.c

 #include "stdio_impl.h"
+#include "libc.h"
 
 static size_t do_read(FILE *f, unsigned char *buf, size_t len)
 {
@@ -13,3 +14,5 @@ int vsscanf(const char *restrict s, const char *restrict fmt, va_list ap)
 	};
 	return vfscanf(&f, fmt, ap);
 }
+
+weak_alias(vsscanf,__isoc99_vsscanf);

src/stdio/vswscanf.c

 #include "stdio_impl.h"
+#include "libc.h"
 #include <wchar.h>
 
 static size_t wstring_read(FILE *f, unsigned char *buf, size_t len)
@@ -34,3 +35,5 @@ int vswscanf(const wchar_t *restrict s, const wchar_t *restrict fmt, va_list ap)
 	};
 	return vfwscanf(&f, fmt, ap);
 }
+
+weak_alias(vswscanf,__isoc99_vswscanf);

src/stdio/vwscanf.c

 #include <stdio.h>
 #include <stdarg.h>
 #include <wchar.h>
+#include "libc.h"
 
 int vwscanf(const wchar_t *restrict fmt, va_list ap)
 {
 	return vfwscanf(stdin, fmt, ap);
 }
+
+weak_alias(vwscanf,__isoc99_vwscanf);

src/stdio/wscanf.c

 #include <stdio.h>
 #include <stdarg.h>
 #include <wchar.h>
+#include "libc.h"
 
 int wscanf(const wchar_t *restrict fmt, ...)
 {
@@ -11,3 +12,5 @@ int wscanf(const wchar_t *restrict fmt, ...)
 	va_end(ap);
 	return ret;
 }
+
+weak_alias(wscanf,__isoc99_wscanf);

src/string/strerror_r.c

 #include <string.h>
 #include <errno.h>
+#include "libc.h"
 
 int strerror_r(int err, char *buf, size_t buflen)
 {
@@ -15,3 +16,5 @@ int strerror_r(int err, char *buf, size_t buflen)
 	memcpy(buf, msg, l+1);
 	return 0;
 }
+
+weak_alias(strerror_r, __xpg_strerror_r);