Fix #98. Fix implemented by merging any reserve multiple into the main

Fix #98.  Fix implemented by merging any reserve multiple into the main
bytecode multiple.

strucsize.asm tests both creation and instantiation of a nested structure.
[1751] and [1752] fix bugs found during the testing of the instantiation
portion of this testcase.

A side effect of this change is that some errors are found in different
phases, and the error messages are slightly different.  Split
reserve-error.asm testcase into two parts to still get full coverage.

svn path=/trunk/yasm/; revision=1753