picotm 0.13.0

• License change: picotm and its modules are now distributed under the terms of the GNU Lesser General Public License, version 3 or later. Test programs and scripts are distributed under the terms of the GNU General Public License, version 3 or later.
• Time/string conversion: The libc module now provides the strftime() and strptime() interfaces from <time.h>.
• Locale support: The libc module now provides support for locale interfaces. This includes setlocale() from ISO and locale_t from POSIX.
• Module-independent pointer-state: The new ptrdata module provides global and thread-local pointer state. Modules can attach state data to a memory address, or retrieve attached state. The locale implementation uses these facilities.
• Mandate stricter error checking during build and in build scripts. The build scripts now compile all source code with -Wall -Werror flags.
• Bug fix: Treemap look-up operations for non-existent entries do no longer result in undefined behavior but return a default value. (#286)