+ 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.
+ modify wgetch() to use the screen which corresponds to its window
parameter rather than relying on SP; some dependent functions still
use SP internally.
+ factor out most use of SP in lib_mouse.c, using parameter.
+ add internal _nc_keyname(), replacing keyname() to associate with a
particular SCREEN rather than the global SP.
+ add internal _nc_unctrl(), replacing unctrl() to associate with a
particular SCREEN rather than the global SP.
+ add internal _nc_tracemouse(), replacing _tracemouse() to eliminate
its associated global buffer _nc_globals.tracemse_buf now in SCREEN.
+ add internal _nc_tracechar(), replacing _tracechar() to use SCREEN in
preference to the global _nc_globals.tracechr_buf buffer.
