gport: Fix build with gcc 4.8 and clang
gport: Fix build with gcc 4.8 and clang

thread_local is a reserved word in gcc 4.8 and clang.
Don't use it as a variable name.

Change-Id: Ia3e6a539ab741ac0f5383c3f6113611a25c6c0de
Signed-off-by: Bernhard Rosenkränzer <0363de98439ff22157633d0b0c13ae8bbe3d448c@linaro.org>

yinquan529/platform-external-gtest,SlimSaber/android_external_gtest,SlimSaber/android_external_gtest,yinquan529/platform-external-gtest,SlimSaber/android_external_gtest,yinquan529/platform-external-gtest