gtest/gmock: bump to version 1.8.0

gtest/gmock: bump to version 1.8.0

GTest version 1.8.0 includes gmock so merge both packages inside gtest

In this merge:

- Add gmock as a suboption of gtest (BR2_PACKAGE_GTEST_GMOCK)
  following advice from Arnout Vandecappelle
- Add BR2_PACKAGE_GMOCK as a legacy entry, selecting BR2_PACKAGE_GTEST
  and BR2_PACKAGE_GTEST_GMOCK.
- Use cmake to install libraries and headers and add missing files
  (gtest.pc, gtest-config, gmock.pc) in
  GTEST_POST_INSTALL_STAGING_HOOKS instead of redefining
  GTEST_INSTALL_STAGING_CMDS
- Remove patch on Python as gmock/gtest now supports python 3.0
  (commit 456fc2b5c4e9ebf05a5987dfe1ff0ac9ffeb53cc)
- Add the correct license in HOST_GTEST_LICENSE as all python code in
  googlemock/scripts/generator is licensed under Apache-2.0 and not
  BSD-3c
- Fix URL of gtest project in Config.in
- Remove the gmock entry from DEVELOPERS
- Install gmock_gen directly, instead of as a symlink to gmock_gen.py

Notice that any external package that depends on gmock will cause an
immediate build termination because make doesn't know how to build
gmock. Since the user has just removed gmock from the legacy menu, it
should be quite obvious what needs to be done.

Signed-off-by: Fabrice Fontaine <fabrice.fontaine@orange.com>
Signed-off-by: Carlos Santos <casantos@datacom.ind.br>
Reviewed-by: Romain Naour <romain.naour@gmail.com>
[Thomas:
 - Use += instead of = when assigning a value to <pkg>_DEPENDENCIES in
   conditional
 - Remove comment about the "tricky logic" around BUILD_GTEST and
   BUILD_GMOCK
 - Move GTEST_GMOCK_INSTALL_MISSING_FILE inside
   the ($(BR2_PACKAGE_GTEST_GMOCK),y) condition.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>