dynamic_bitset: in dyn_bitset_unit_tests1.cpp, replaced very ill-thought assert() with more sensible code to check for "negative sizes"

[SVN r48729]

libs/dynamic_bitset

@@ -1 +1 @@
-Subproject commit 24d2081a731c07a9e22807b16c9975368bae409d
+Subproject commit 7ed46a666780e472e68984faae891f3d300633a4