OCE_DISABLE_X11 should not be defined when using cocoa

Fix #493.
Set install RPATH in TKernel

GNU ld has a new-dtags feature which inserts DT_RUNPATH section instead
of DT_RPATH section in ELF shared libraries. Unlike DT_RPATH, DT_RUNPATH
is not transitive.
Draw plugins are loaded by OSD_SharedLibrary::DlOpen, this is why library
paths must be hardcoded into TKernel.

As TKernel does not depend on other libraries, no RPATH section is
automatically inserted by CMake.  To workaround this, INSTALL_RPATH
and BUILD_WITH_INSTALL_RPATH properties of TKernel are explicitly set.

The new OCE_TKERNEL_BUILD_WITH_INSTALL_RPATH option is provided; it is
ON by default, and can be disabled if this change causes trouble.

Fix #483.
Set OCE_TESTING option ON by default

Do not mark it as advanced.
[mingw-warning-fix][maybe-uninitialized]

If Abs(Coord - Arr(i)) == Tol here in Hunt(), then it's possible for the variable that Iloc references to be uninitialized without raising an error. Hunt() is used in Locate2Coord() defined later on in the file, and it's possible for the variable N there to be used in comparisons without being initialized.
[mingw-warning-fix][array-bounds]

MinGW thinks it's possible to exceed the array bounds on line 898; it's not clear to me whether or not this is possible after looking at the code. This addition shouldn't hurt anything anyway.
Fix gl2ps libraries installation.
[clang-warning-fix][logical-not-parentheses]

Since gce_Done is an enumerated type, what's there makes no sense at all
and was surely meant to be what I've changed it to.
[intel-warning-fix][unknown-pragma]

The Intel compiler complains about the OpenMP pragmas, so I wrapped them
in ifdef's.
[intel-warning-fix][tmpnam-dangerous]

mkdtemp creates directories with the permission set 0700 and has no
option to directly set alternate permissions, while Protect.Internal()
is equivalent to 0644. mkdtemp still obeys umask though and the result
permissions will be equivalent to: 0700 & ~umask & 0777 == 0600. So
basically the previous version created directories with 0644, and this
version will create them with 0600. I think this is okay because the
unlink call causes the temporary directory to be destroyed after the
current process finishes; there's no need for anyone else but owner (the
0x00 bit) to have access to it anyway.
[clang-warning-fix][tmpnam-dangerous]

Clang 3.5 reports using tmpnam() as dangerous and to use mkstemp() instead. I believe this change will produce the same behavior as the original code but not 100% sure as I'm not very familiar with POSIX-only functions.
Remove remnants of libxmu

This was discussed in #418 and removed from CMakeLists.txt here:
https://github.com/tpaviot/oce/commit/94534353bc7a27790596d0f4af57d7c221cea154
Apply patches from c1eb693 on OCCT 6.7.1
Update dependencies of TKQADraw
Bump OCCT version number in README.md to 6.7.1
Fix installation of resource files for DRAW

Add src/TObj/TObj.msg, and remove several files which do
no more exist.
Merge pull request #499 from tpaviot/review/occt671

Upgrade to OCCT 6.7.1
Merge pull request #497 from heyuqi/master

Fix gl2ps libraries installation.
Merge pull request #498 from tpaviot/review/remove-xmu-remnants

Remove remnants of libxmu
Merge pull request #494 from tpaviot/review/no-DISABLE_X11-with-cocoa

OCE_DISABLE_X11 should not be defined when using cocoa
Merge pull request #492 from tpaviot/review/misc-warning-fixes

Misc. warning fixes