Further trim the psx headers and support easy vendoring.

Remove psx_pthread_create() from libpsx - given the way -lpsx is
linked this is not needed.

Also, as pointed out by Lorenz Bauer, "go mod vendor" support
was unable to vendor a copy of psx_syscall.h because it didn't
reside in the same directory as the *.go code for the psx package.
(General discussion golang/go#26366 .)
Given that we can, avoid the use of a sub-directory in the libcap
tree.

Signed-off-by: Andrew G. Morgan <morgan@kernel.org>

Author: AndrewGMorgan

Diff for: go/Makefile

@@ -104,9 +104,8 @@ endif
 
 install: all
 	rm -rf $(FAKEROOT)$(GOPKGDIR)/$(IMPORTDIR)/psx
-	mkdir -p $(FAKEROOT)$(GOPKGDIR)/$(IMPORTDIR)/psx/include/sys
-	for x in src/$(IMPORTDIR)/psx/* ; do if [ -d $$x ]; then continue; fi; install -m 0644 $$x $(FAKEROOT)$(GOPKGDIR)/$(IMPORTDIR)/psx; done
-	install -m 0644 src/$(IMPORTDIR)/psx/include/sys/psx_syscall.h $(FAKEROOT)$(GOPKGDIR)/$(IMPORTDIR)/psx/include/sys/psx_syscall.h
+	mkdir -p $(FAKEROOT)$(GOPKGDIR)/$(IMPORTDIR)/psx
+	install -m 0644 src/$(IMPORTDIR)/psx/* $(FAKEROOT)$(GOPKGDIR)/$(IMPORTDIR)/psx
 	mkdir -p $(FAKEROOT)$(GOPKGDIR)/$(IMPORTDIR)/cap
 	rm -rf $(FAKEROOT)$(GOPKGDIR)/$(IMPORTDIR)/cap/*
 	install -m 0644 src/$(IMPORTDIR)/cap/* $(FAKEROOT)$(GOPKGDIR)/$(IMPORTDIR)/cap

Diff for: libcap/include/sys/psx_syscall.h

@@ -1 +1 @@
-../../../psx/include/sys/psx_syscall.h
+../../../psx/psx_syscall.h

Diff for: libcap/psx_syscall.h

@@ -0,0 +1 @@
+include/sys/psx_syscall.h

Diff for: psx/psx.c

@@ -25,9 +25,10 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
-#include <sys/psx_syscall.h>
 #include <sys/syscall.h>
 
+#include "psx_syscall.h"
+
 /*
  * psx_load_syscalls() is weakly defined so we can have it overridden
  * by libpsx if it is linked. Specifically, when libcap calls
@@ -486,16 +487,6 @@ int __wrap_pthread_create(pthread_t *thread, const pthread_attr_t *attr,
     return ret;
 }
 
-/*
- * psx_pthread_create is a wrapper for pthread_create() that registers
- * the newly created thread. If your threads are created already, they
- * can be individually registered with psx_register().
- */
-int psx_pthread_create(pthread_t *thread, const pthread_attr_t *attr,
-		       void *(*start_routine) (void *), void *arg) {
-    return __wrap_pthread_create(thread, attr, start_routine, arg);
-}
-
 /*
  * __psx_immediate_syscall does one syscall using the current
  * process.

Diff for: psx/psx.go

@@ -55,11 +55,10 @@ import (
 	"syscall"
 )
 
-// #cgo CFLAGS: -I${SRCDIR}/include
 // #cgo LDFLAGS: -lpthread -Wl,-wrap,pthread_create
 //
 // #include <errno.h>
-// #include <sys/psx_syscall.h>
+// #include "psx_syscall.h"
 //
 // long __errno_too(long set_errno) {
 //     long v = errno;

Diff for: psx/include/sys/psx_syscall.h renamed to psx/psx_syscall.h

@@ -51,23 +51,6 @@ long int psx_syscall6(long int syscall_nr,
 		      long int arg1, long int arg2, long int arg3,
 		      long int arg4, long int arg5, long int arg6);
 
-/*
- * psx_pthread_create() wraps the -lpthread pthread_create() function
- * call and registers the generated thread with the psx_syscall
- * infrastructure.
- *
- * Note, to transparently redirect all the pthread_create() calls in
- * your binary to psx_pthread_create(), link with:
- *
- *   gcc ... -lpsx -lpthread -Wl,-wrap,pthread_create
- *
- * [That is, libpsx contains an internal definition for the
- * __wrap_pthread_create function to invoke psx_pthread_create
- * functionality instead.]
- */
-int psx_pthread_create(pthread_t *thread, const pthread_attr_t *attr,
-		       void *(*start_routine) (void *), void *arg);
-
 /*
  * This function should be used by systems to obtain pointers to the
  * two syscall functions provided by the PSX library. A linkage trick