Revert "lib{c,sys}: normalize export of openat, setcontext, and swapc…

…ontext"

I put the symbols in the wrong file (should have been
lib/libc/sys/Symbol.map), added a duplicate pdfork entry due to a botch
rebase, and there seems to be a issue with gcc13/binutils not exposing
the symbols so revert the whole thing while I debug.

This reverts commit ee632fb.

lib/libc/sys/setcontext.c

@@ -36,6 +36,7 @@
 __weak_reference(__sys_setcontext, __setcontext);
 __sym_compat(setcontext, __impl_setcontext, FBSD_1.0);
 __weak_reference(setcontext, __impl_setcontext);
+__sym_default(setcontext, setcontext, FBSD_1.2);
 
 #pragma weak setcontext
 int

lib/libc/sys/swapcontext.c

@@ -38,6 +38,7 @@
 __weak_reference(__sys_swapcontext, __swapcontext);
 __sym_compat(swapcontext, __impl_swapcontext, FBSD_1.0);
 __weak_reference(swapcontext, __impl_swapcontext);
+__sym_default(swapcontext, swapcontext, FBSD_1.2);
 
 #pragma weak swapcontext
 int

lib/libsys/Symbol.sys.map

@@ -301,8 +301,6 @@ FBSD_1.2 {
 	cap_getmode;
 	getloginclass;
 	getpagesizes;
-	openat;
-	pdfork;
 	pdgetpid;
 	pdkill;
 	posix_fallocate;
@@ -311,9 +309,7 @@ FBSD_1.2 {
 	rctl_get_limits;
 	rctl_add_rule;
 	rctl_remove_rule;
-	setcontext;
 	setloginclass;
-	swapcontext;
 };
 
 FBSD_1.3 {

lib/libsys/openat.c

@@ -52,6 +52,7 @@ __weak_reference(_openat, __openat);
 #endif
 __sym_compat(openat, __impl_openat, FBSD_1.1);
 __weak_reference(openat, __impl_openat);
+__sym_default(openat, openat, FBSD_1.2);
 
 #pragma weak openat
 int