configure: use AC_USE_SYSTEM_EXTENSIONS to determine features

The AC_USE_SYSTEM_EXTENSIONS will enable everything that a system allows
to be enabled, so there is no longer need for a source file specific
*_SOURCE definitions.  Secondly the uses of _BSD_SOURCE that are removed
in this change are part of deprecated API.  See reference link for
details.

Reference: https://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commit;h=c941736c92fa3a319221f65f6755659b2a5e0a20
Signed-off-by: Sami Kerola <kerolasa@iki.fi>

configure.ac

@@ -18,6 +18,7 @@ AC_CONFIG_FILES([
 ])
 AC_CONFIG_SRCDIR([src/main.cpp])
 AC_CONFIG_MACRO_DIR([m4])
+AC_USE_SYSTEM_EXTENSIONS
 AC_CONFIG_HEADERS([config.h])
 GETTEXT_PACKAGE=powertop
 AC_SUBST([GETTEXT_PACKAGE])

src/report/report-formatter-base.cpp

@@ -23,8 +23,6 @@
  * Written by Igor Zhbanov <i.zhbanov@samsung.com>
  * 2012.10 */
 
-#define _BSD_SOURCE
-
 /* Uncomment to disable asserts */
 /*#define NDEBUG*/
 

src/report/report-formatter-csv.cpp

@@ -23,8 +23,6 @@
  * Written by Igor Zhbanov <i.zhbanov@samsung.com>
  * 2012.10 */
 
-#define _BSD_SOURCE
-
 /* Uncomment to disable asserts */
 /*#define NDEBUG*/
 

src/report/report-formatter-html.cpp

@@ -23,8 +23,6 @@
  * Written by Igor Zhbanov <i.zhbanov@samsung.com>
  * 2012.10 */
 
-#define _BSD_SOURCE
-
 /* Uncomment to disable asserts */
 /*#define NDEBUG*/