Make relevant methods in BC_Hash use 'const char *' instead of 'char *'.

This brings CV more in line with HV where this change
already took place, and reduces the number of warnings about writable
constant strings.  It also will reduce the amount of work needed to
synchronize the plugin API between CV and HV. The change propagate
to the class StringFile as well.
Make plugin_title() return 'const char *' instead of 'char *'

This bring CV more in line with HV version 4.5 where this change
already took place, and reduce the number of warnings about writable
constant strings.  The change propagate to the classes BC_Window
and BC_WindowBase title as well.
Rewrite *printf() calls without a format string to avoid potential security issue.

This fixes issues causing build errors triggered by the compiler flags
"-Wformat -Werror=format-security"
Fix typo in fprintf() call in void ArrayList<TYPE>::remove_object_number().

Fixes warning discovered by -Wformat.
Make relevant methods in BC_Signals use 'const char *' instead of 'char *'.

This bring CV more in line with HV version 4 where this change
already took place, and reduce the number of warnings about writable
constant strings.
Quicker initialization of empty strings (s[0]=0; instead of sprintf(s,""); )

Use s[0]=0 instead of sprintf(s,) to null terminate an empty string.
Get rid of warning: zero-length gnu_printf format string [-Wformat-zero-length].
Rename configure.in to configure.ac
Tell git to ignore more generated files
Merge branch 'master' into from-cinelerra-hv-4.5-const-bc-signals