unistr/u8-pcpy, unistr/u16-pcpy, unistr/u32-pcpy: New modules.
* lib/unistr.in.h (u8_pcpy, u16_pcpy, u32_pcpy): New declarations.
* lib/unistr/u-pcpy.h: New file, based on lib/wmempcpy.c.
* lib/unistr/u8-pcpy.c: New file, based on lib/unistr/u8-cpy.c.
* lib/unistr/u16-pcpy.c: New file, based on lib/unistr/u16-cpy.c.
* lib/unistr/u32-pcpy.c: New file, based on lib/unistr/u32-cpy.c.
* modules/unistr/u8-pcpy: New file, based on modules/unistr/u8-cpy.
* modules/unistr/u16-pcpy: New file, based on modules/unistr/u16-cpy.
* modules/unistr/u32-pcpy: New file, based on modules/unistr/u32-cpy.