MFC r259053:

Pull in r196590 from upstream clang trunk (by rdivacky):

  Move the body of GCCInstallationDetector ctor into an init() function
  and call it from its only user. The linux toolchain. This saves quite
  a lot of directory searching on other platforms.

See http://docs.freebsd.org/cgi/mid.cgi?51E6FAF5.3080802 for the
original discussion.  With this fix, the search for gcc installations is
completely eliminated on FreeBSD.

Reported by:	Kurt Lidl <lidl@pix.net>
MFC r259083:

For WARNS <= 3, change the clang warning flag -Wno-conversion to
-Wno-enum-conversion.  In earlier clang versions (before 3.2), the
latter did not exist, and suppressing enum conversion warnings was
really the goal of this warning suppression flag.

This should enable the same kind of warning again as was fixed by
r259072 ("incompatible integer to pointer conversion passing 'Elf_Addr'
(aka 'unsigned int') to parameter of type 'void *'"), and which was only
emitted by gcc.

Noticed by:	kib
Hand merge from current r235717:
Implement pmap_mincore for arm.  Now programs using it don't cause a
flood of console messages.

Reviewed by:	alc@
MFC: r257598
During code inspection, I spotted that there was a code path where
CLNT_CONTROL() would be called on "client" after it was
released via CLNT_RELEASE(). It was unlikely that this
code path gets executed and I have not heard of any problem
report caused by this bug. This patch fixes the code so that
this cannot happen.
[automated] Merge in upstream-github/stable/9