tests: Fix build on x86_gcc2

This patch fixes the build of unittests on x86_gcc2.

src/tests/kits/shared/KeymapTest.cpp:
* Don't use auto
* Don't use braced-initialization for std::map.

src/tests/system/kernel/vm/Jamfile:
* Link lock.o from kernel source to include _mutex_lock and
_mutex_unlock when linking libkernelvmtest.so

Change-Id: I60e02bfb23334064ec25d767f659a188e393ed1c
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2074
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

BKeymap: Add unit tests and fix issues

Add a preliminary set of unit tests for BKeymap and fix these issues:

* BKeymap::operator=() caused a crash by allocating a zero-byte array to hold
the other object's character data.
* BKeymap::SetToCurrent() and SetToDefault() leaked memory by not freeing an
existing character array before allocating a new one.
* BKeymap::SetToCurrent() incorrectly determined the size of the current
keymap's character array, causing GetChars() to fail whenever the current
keymap was loaded. Now SetToCurrent() uses the _get_key_map() private
function, which accurately reports the size of the array.

This commit also updates a Jamfile by replacing a use of "UseHeaders" to
include private header files with the more concise and expressive
"UsePrivateHeaders".

Change-Id: If6f71b209f1bd395be57835c4dd89f0e3f845994
Reviewed-on: https://review.haiku-os.org/c/haiku/+/1724
Reviewed-by: Ryan Leavengood <leavengood@gmail.com>
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>
Reviewed-by: Stephan Aßmus <superstippi@gmx.de>