chg non-standard __UNIX__ to (hopefully) standard __unix__ in plugin.cpp,...

chg non-standard __UNIX__ to (hopefully) standard __unix__ in plugin.cpp, fixes maca issues on Ubuntu

libpwrutils/plugin.cpp

@@ -13,7 +13,7 @@ or FITNESS FOR A PARTICULAR PURPOSE.
     See the LICENCE, COPYING.LESSER and COPYING files for more details.
 */
 #include <libpwrutils/plugin.h>
-#ifdef __UNIX__
+#ifdef __unix__
 #include <dlfcn.h>
 #endif
 #include <iostream>
@@ -32,7 +32,7 @@ std::string make_soname(const std::string &scope, const std::string &name)
 
 bool load(const std::string &scope, const std::string &name, bool quiet)
 {
-#ifdef __UNIX__
+#ifdef __unix__
 	std::string soname = make_soname(scope, name);
 	// std::cerr << "PLUGIN LOAD " << scope << " " << name << " " << soname << "\n";
 	// first check if the plugin was already loaded
@@ -75,7 +75,7 @@ bool load(const std::string &scope, const std::string &name, bool quiet)
 bool load_check(const std::string &scope, const std::string &name, bool quiet,
 		boost::function<size_t (void)> counter, const std::string &what)
 {
-#ifdef __UNIX__
+#ifdef __unix__
 	size_t before = counter();
 	if (load(scope, name, quiet)) {
 		size_t after = counter();