[PECOFF] Align .edata fields on natural boundaries.

The only data in .edata whose length varies is the string. This patch moves
all the strings to the end of the section, so that 16-bit or 32-bit integers
are aligned on correct boundaries.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@197213 91177308-0d34-0410-b5e6-96231b3b80d8