Added KDevelop and GCC PCH files to the .gitignore file.
Merge pull request #528 from OvermindDL1/gitignore_additions

Added KDevelop and GCC PCH files to the .gitignore file.
Add initial support for 64-bit Android ABIs.
For Travis CI - double the time to wait for AVD to start.
AVD with API level 21 seems to take longer to start. Also when the AVD failed to start in time, CI now skips the APK installation/launching test and considers the whole build as passed.
Fix Android toolchain so that Clang always comes after GCC.
Merge some of the changes from one of the android-cmake's PR for NDK r10c.
For Travis CI - attempt to fix failure to start emulator with API 21.
For Travis CI - reduce the AVD waiting time to 1 minutes instead.
There is no point to wait for AVD to start. By the time the CI finishes the build, if the emulator is able to start the AVD then it should have been already done so.
On non-CI environment, the build time could still be much faster than the emulator starting the AVD, thus the function to wait for AVD is still useful in non-CI environment.
For Travis CI - switch CI build to use Android build environment.