libstdc++: Avoid bogus overflow warnings in std::vector<bool> [PR110807]

GCC thinks the allocation can alter the object being copied if it's
globally reachable, so doesn't realize that [x.begin(), x.end()) after
the allocation is the same as x.size() before it.

This causes a testsuite failure when testing with -D_GLIBCXX_DEBUG:
FAIL: 23_containers/vector/bool/swap.cc (test for excess errors)
A fix is to move the calls to x.begin() and x.end() to before the
allocation.

A similar problem exists in vector<bool>::_M_insert_range where *this is
globally reachable, as reported in PR libstdc++/110807. That can also be
fixed by moving calls to begin() and end() before the allocation.

libstdc++-v3/ChangeLog:

	PR libstdc++/110807
	* include/bits/stl_bvector.h (vector(const vector&)): Access
	iterators before allocating.
	* include/bits/vector.tcc (vector<bool>::_M_insert_range):
	Likewise.
	* testsuite/23_containers/vector/bool/110807.cc: New test.