common: Cleanup the use of USE_NPTH and HAVE_NPTH macros.
* configure.ac (HAVE_NPTH): New ac_define. * common/estream.c: Use USE_NPTH instead of HAVE_NPTH. * common/http.c: Ditto. Replace remaining calls to pth by npth calls. (connect_server): Remove useless _(). * common/exechelp-posix.c, common/exechelp-w32.c * common/exechelp-w32ce.c: Use HAVE_PTH to include npth.h. * common/init.c (_init_common_subsystems): Remove call to pth_init. * common/sysutils.c (gnupg_sleep): Use npth_sleep. * scd/ccid-driver.c (my_sleep): Ditto.
USE_NPTH is used in case were we may build with and without nPth. The
missing definition HAVE_NPTH didn't allowed us to build outher sources
with nPTh support.