Fix pedantic warnings

With the latest build system, somehow -Wpedantic got turned on.  This is
reasonable given that we expect this code to compile against a number of
targets.  Fix void issues.

void function() changes to void function(void)

Change-Id: I89a2dcbcd88c7d163ffdfb67927f71b39cb7aa6f
Signed-off-by: Ed Tanous <etanous@nvidia.com>
diff --git a/meson.build b/meson.build
index ede0bf1..6316995 100644
--- a/meson.build
+++ b/meson.build
@@ -18,6 +18,7 @@
         '-DLIBCPER_EXAMPLES="' + example_dir + '"',
         '-DLIBCPER_JSON_SPEC="' + spec_dir + '"',
         '-D_POSIX_C_SOURCE=200809L',
+        '-Wno-gnu-statement-expression-from-macro-expansion',
     ],
     language: 'c',
 )