+ add configure option --enable-weak-symbols to turn on new feature.
+ add configure-check for availability of weak symbols.
+ modify linkage with pthread library to use weak symbols so that
applications not linked to that library will not use the mutexes,
etc. This relies on gcc, and may be platform-specific (patch by Dr
Werner Fink).
+ add note to INSTALL to document limitation of renaming of tic library
using the --with-ticlib configure option (report by Dr Werner Fink).
+ document (in manpage) why tputs does not detect I/O errors (prompted
by comments by Samuel Thibault).
+ fix remaining warnings from Klocwork report.