[ci skip]

Use enum to specify flag value type.

It is possible to create a type-safe version of FlagRegisterer
ctor (as well as some internal gflags classes), that will deduce
type of the new flag automatically.

This results in removing quite a few calls to strcmp() when new
flag is created.

No existing behavior change.

Fix incorrect flag value typename for uint32.

Add missing reference symbol to a function parameter.

fix: Consider Windows-style LRLF in flag parsing

Fix bazel build

complain config.h can't be found.

Add GFLAGS_IS_A_DLL compile option for unit test which includes private config.h.

Support uint32 as flag type

From #99, “Given that there is an unsigned flag type for 64-bit
integers, it is probably reasonable to request/expect the same for
32-bit integers.”

fix #133: Use awk instead of sed which would require different options on OS X