all: Update reserved function names

Update reserved function names starting with one underscore, replacing
them as follows:
   '_k_' with 'z_'
   '_K_' with 'Z_'
   '_handler_' with 'z_handl_'
   '_Cstart' with 'z_cstart'
   '_Swap' with 'z_swap'

This renaming is done on both global and those static function names
in kernel/include and include/. Other static function names in kernel/
are renamed by removing the leading underscore. Other function names
not starting with any prefix listed above are renamed starting with
a 'z_' or 'Z_' prefix.

Function names starting with two or three leading underscores are not
automatcally renamed since these names will collide with the variants
with two or three leading underscores.

Various generator scripts have also been updated as well as perf,
linker and usb files. These are
   drivers/serial/uart_handlers.c
   include/linker/kobject-text.ld
   kernel/include/syscall_handler.h
   scripts/gen_kobject_list.py
   scripts/gen_syscall_header.py

Signed-off-by: Patrik Flykt <patrik.flykt@intel.com>

drivers/timer/hpet.c

@@ -141,7 +141,7 @@ u32_t z_clock_elapsed(void)
 	return ret;
 }
 
-u32_t _timer_cycle_get_32(void)
+u32_t z_timer_cycle_get_32(void)
 {
 	return MAIN_COUNTER_REG;
 }