Increase nptl test case buffer size so we really block on current Linux kernels.

	* tst-cancel4.c (WRITE_BUFFER_SIZE): Increase to 16384.
PowerPC: use _dl_static_init to set GLRO(gl_pagesize)

This patch fixes dlfcn/tststatic5 for PowerPC where pagesize
variable was not properly initialized in certain cases. This patch
is based on other architecture code.
Remove Linux kernel version ambiguity in comment added by previous commit.

	* tst-cancel4.c (WRITE_BUFFER_SIZE): Adjust comment.