v1.1.2

Small source improvements since v1.1.0:

• Add explicit qualifier to ctors of some objects
• Rename DEFAULT_CHARSET macro which clashed with a windows macro
• Rename SPIRIT_PO_NOEXCEPT to SPIRIT_PO_NO_EXCEPTIONS. There is some compat code to detect the old form, but the old form isn't documented now. See commit message for the rationale for this change.

Besides this, there was a rewrite of some sections of documentation.