jit documentation fixes

jit documentation fixes

gcc/jit/ChangeLog:
	* docs/cp/intro/tutorial03.rst: Add missing arguments to
	gccjit::block::end_with_conditional call.  Add on_true/on_false
	comments.  Tweak the wording.
	* docs/intro/tutorial03.rst: Add missing arguments to
	gcc_jit_block_end_with_conditional call.  Add some clarifying
	comments.
	* docs/topics/compilation.rst: Tweak the wording to avoid an
	ambiguous use of "this".
	* docs/topics/contexts.rst: Fix a typo.
	* docs/topics/expressions.rst (GCC_JIT_BINARY_OP_MINUS): Remove
	a stray backtick.
	* docs/_build/texinfo/libgccjit.texi: Regenerate.

From-SVN: r221218