Style tidy.
premake_common: default to -std=c++11 under Linux; only use -Werror with Clang.
DescData: prevent warning from GCC in sanity assertion¹.

1: -Wtype-limits.
serialize: The Pedant: SEMICOLON IN MY ENUM MEMBER.
test/desc/serialize: prevent uninitialized warning from GCC¹’².

1: -Wmissing-field-initializers.
2: P.S.
	GCC doesn't really work right now anyways. It can't deduce the
	implicit DescCompoundRef ctor when constructing a RefDesc.