doc: Switch references from pkg-config to pkgconf

The former used to be the reference implementation, but it has been
stagnant to the point of not showing much signs of life. Switch to
the currently active and more complete implementation for references.

man/libbsd.7

@@ -42,7 +42,7 @@ The library can be used in an overlay mode, which is the preferred way, so
 that the code is portable and requires no modification to the original BSD
 code.
 This can be done easily with the
-.Xr pkg-config 1
+.Xr pkgconf 1
 library named
 .Pa libbsd-overlay .
 Or by adding the system-specific include directory with the
@@ -64,7 +64,7 @@ this is less portable as it makes using
 mandatory and it will not work on BSD-based systems, and requires
 modifying original BSD code.
 This can be done with the
-.Xr pkg-config 1
+.Xr pkgconf 1
 library named
 .Pa libbsd .
 The includes in this case should be namespaced with
@@ -79,7 +79,7 @@ program so that the
 .Fn setproctitle_init 3
 function gets invoked automatically at startup time.
 This can be done with the
-.Xr pkg-config 1
+.Xr pkgconf 1
 library named
 .Pa libbsd-ctor .
 .Sh HEADERS

man/setproctitle.3bsd

@@ -54,7 +54,7 @@ library routine only needs to be called (before any call to
 and with
 .Fn main
 arguments), if the automatic constructor support has not
-been linked in through the libbsd-ctor pkg-config file.
+been linked in through the libbsd-ctor pkgconf file.
 .Pp
 The title is set from the executable's name, followed by the
 result of a

src/setproctitle_ctor.c

@@ -38,7 +38,7 @@
  *
  * To avoid any other possible fallout, the constructor is split into a
  * new static library that needs to be linked explicitly into programs
- * using setproctitle(). As an additional safety measure the pkg-config
+ * using setproctitle(). As an additional safety measure the pkgconf(1)
  * linker flags will mark the program as not allowing to be dlopen()ed
  * so that we make sure to avoid the problem described above.
  */