various fixes for clean build and test on win32; configpm broken,

various fixes for clean build and test on win32; configpm broken,
needed to open myconfig.SH rather than myconfig; sundry adjustments
to bytecode stuff; tweaks to DYNAMIC_ENV_FETCH code to make it
work under win32; getenv_sv() changed to getenv_len() since SVs
aren't visible in the lower echelons; remove bogus exports from
config.sym; PERL_OBJECT-ness for C++ exception support; null out
IoDIRP in filter_del() or sv_free() will attempt to close it

p4raw-id: //depot/perl@3387