Build with pedantically standard C++ (#1309)

* Remove array designators (not standard C++)

* Build with pedantically standard C++

Makefile

@@ -25,8 +25,8 @@ PNGLDLIBS	:= `${PKG_CONFIG} --libs-only-l libpng`
 # Note: if this comes up empty, `version.cpp` will automatically fall back to last release number
 VERSION_STRING	:= `git --git-dir=.git describe --tags --dirty --always 2>/dev/null`
 
-# TODO: use -pedantic after non-C++ idioms are gone
-WARNFLAGS	:= -Wall -Wno-unknown-warning-option -Wno-c99-designator
+WARNFLAGS	:= -Wall -pedantic -Wno-unknown-warning-option \
+                   -Wno-gnu-zero-variadic-macro-arguments
 
 # Overridable CXXFLAGS
 CXXFLAGS	?= -O3 -flto -DNDEBUG