Attempt to fix #include on Windows

Similar to 78db6a6c923da8c5495b2482ca018a882bec17bc.
third_party/lzma_sdk/ is gone
Drop the unmaintained scons build file
More unused files
[cmap] Fix format 13 parsing and serializing

Language is 32bit in format-13 subtable, not 16bit.
[cmap] Allow fonts that only have a format-12 or format-13 subtable
Make Process() a method of ots::OTSContext

Makes it easier to access the context’s private members without the ugly
getters.
Fix crash

It makes no sense to access “it->first” if “it == table_map.end()”, a
thinko introduced in 9f5b6e2e6a5c0182e4c89233aff8a4f6414d55e0.
Simplify
#undef the TABLE_NAME and DROP_THIS_TABLE macros at the end of each file that uses them
winstall
updates the INSTALL documentation for building OTS with zlib as third_party include on Windows