tools/cmake: Update to 3.15.1

Update CMake to 3.15.1
Refresh patches
Remove inofficial fossies.org and replace with GitHub (link on official site)
Remove 150-C-feature-checks-Match-warnings-more-strictly.patch as it's
a no longer needed backport from upstream.
Disable ccache if GCC is 4.8, 4.9 or 5.X to avoid build failures.
Reference: https://github.com/openwrt/openwrt/pull/1929

Signed-off-by: Daniel Engberg <daniel.engberg.lists@pyret.net>

tools/cmake/patches/130-bootstrap_parallel_make_flag.patch

@@ -1,6 +1,6 @@
 --- a/bootstrap
 +++ b/bootstrap
-@@ -1164,7 +1164,10 @@ int main(){ printf("1%c", (char)0x0a); r
+@@ -1168,7 +1168,10 @@ int main(){ printf("1%c", (char)0x0a); r
  ' > "test.c"
  cmake_original_make_flags="${cmake_make_flags}"
  if [ "x${cmake_parallel_make}" != "x" ]; then