Fix warning about initialization order.
Fix warnings about unused value in JSONTEST_ASSERT_PRED.

Fix warnings:

src/test_lib_json/main.cpp:156:60: warning: value computed is not used [-Wunused-value]
src/test_lib_json/main.cpp:156:60: warning: statement has no effect [-Wunused-value]
src/test_lib_json/main.cpp:157:61: warning: value computed is not used [-Wunused-value]
src/test_lib_json/main.cpp:157:61: warning: statement has no effect [-Wunused-value]
....
Fix warnings about signed/unsigned integer comparisons.
Merge branch 'Warnings'

Fix warnings that occur with -Wall with GCC 4.6.3.
Merge branch 'master' of github.com:TubeTK/jsoncpp-cmake