This release fixes a few bugs in the configuration of gflags_declare.h
and adds a GFLAGS_INCLUDE_DIR variable to the build configuration.
Setting GFLAGS_NAMESPACE to "google" no longer changes also the include
path of the public header files. This allows the use of the library with
other Google projects such as glog which still use the deprecated "google"
namespace for the gflags library, but include it as "gflags/gflags.h".