Fixed the build error in routing tests.

Review: https://reviews.apache.org/r/24902
Fixed MesosContainerizer to reject tasks that have ContainerInfo set.

Review: https://reviews.apache.org/r/25033
Log the uid and pid when receiving a SIGTERM.

Review: https://reviews.apache.org/r/24700
Refactored the JSON output streaming.

Review: https://reviews.apache.org/r/24877
Adjustments for new JSON streaming.

Review: https://reviews.apache.org/r/25053
Added logging when master/slaves/frameworks bind to loopback address.

Review: https://reviews.apache.org/r/25055
Fixed timed_tests.sh script to preserve exit status of the test.
Use curl-config to locate lib curl when possible

If libcurl.a is located on a non-standard path, the test for libcurl in the configure script fails, even if the path is specified in LDFLAGS.

To work around this we can use curl-config to provide the needed path and link options to the compiler.

This patch modifies configure.ac to check for curl-config and use its output as an argument to AC\_CHECK\_LIB if possible.

Review: https://reviews.apache.org/r/24407
Minor style fixes from: https://reviews.apache.org/r/24407/
Removed duplicate headers imports

Review: https://reviews.apache.org/r/25042
Replaced PKG_CHECK_MODULES with AC_CHECKs in configure.ac.

Review: https://reviews.apache.org/r/25030
Replaced PKG_CHECK_MODULES with AC_CHECKs in libprocess configure.ac.

Review: https://reviews.apache.org/r/25031
Fixed signal handling for stout.

Review: https://reviews.apache.org/r/25126
Fixed signal handling in libprocess.

Review: https://reviews.apache.org/r/25128
Fixed signal handling for Mesos.

Review: https://reviews.apache.org/r/25129
Improved the signal handling comment in Mesos tests.
Fix External Containerizer creation.

Review: https://reviews.apache.org/r/25116
Modifed execute cli to run docker images.

Review: https://reviews.apache.org/r/24808
require some c++11 features for libprocess

Review: https://reviews.apache.org/r/25168
require some c++11 features for mesos

Review: https://reviews.apache.org/r/25169