Port to npth.

* configure.ac: Don't check for PTH but for NPTH.
(AH_BOTTOM): Remove PTH_SYSCALL_SOFT.
(have_pth): Rename to ...
(have_npth): ... this.
(USE_GNU_NPTH): Rename to ...
(USE_GNU_PTH): ... this.
* m4/npth.m4: New file.
* agent/Makefile.am, agent/cache.c, agent/call-pinentry.c,
agent/call-scd.c, agent/findkey.c, agent/gpg-agent.c,
agent/trustlist.c, common/Makefile.am, common/estream.c,
common/exechelp-posix.c, common/exechelp-w32.c,
common/exechelp-w32ce.c, common/http.c, common/init.c,
common/sysutils.c, dirmngr/Makefile.am, dirmngr/crlfetch.c,
dirmngr/dirmngr.c, dirmngr/dirmngr_ldap.c, dirmngr/ldap-wrapper-ce.c,
dirmngr/ldap-wrapper.c, dirmngr/ldap.c, g13/Makefile.am,
g13/call-gpg.c, g13/g13.c, g13/runner.c, scd/Makefile.am,
scd/apdu.c, scd/app.c, scd/ccid-driver.c, scd/command.c,
scd/scdaemon.c, tools/Makefile.am: Port to npth.

dirmngr/dirmngr_ldap.c

@@ -33,7 +33,7 @@
 #include <sys/time.h>
 #include <unistd.h>
 #ifndef USE_LDAPWRAPPER
-# include <pth.h>
+# include <npth.h>
 #endif
 
 #ifdef HAVE_W32_SYSTEM