travis: drop precise distro jobs

The precise distro is marked deprecated in travis and will be dropped
entirely in 2 months time.
Reviewed-by: NAndrea Bolognani <abologna@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

.travis.yml

@@ -4,12 +4,8 @@ cache: ccache
 
 matrix:
   include:
-    - compiler: gcc
-      dist: precise
     - compiler: gcc
       dist: trusty
-    - compiler: clang
-      dist: precise
     - compiler: clang
       dist: trusty
     - compiler: clang
@@ -89,9 +85,6 @@ env:
     # The custom $PATH is just to pick up some extra binaries installed
     # through homebrew on macOS and it's completely harmless on Linux
     - PATH="/usr/local/opt/gettext/bin:/usr/local/opt/rpcgen/bin:$PATH"
-    # The hyperv driver fails to build with clang on precise due to this
-    # error being raised in one of openwsman header files
-    - CFLAGS="-Wno-error=variadic-macros"
     - VIR_TEST_DEBUG=1
 
 before_install: