Post-merge fix of the fixes for NPTL configuration (bug#2173, bug#5871, and bug#9497).
config/ac-macros/openssl.m4:
"Configure" variable 'IS_LINUX' renamed to 'TARGET_LINUX'.
Manual merge: In 4.1, this was in 'acinclude.m4'.
include/my_global.h:
As we have a new CPP symbol, this should be "undef"ed explicitly.