Use -mrtd and -mregparm=3 to reduce the generated code sizes.
This means that any missing prototypes could be fatal. Also, you
must take care when writing assembly code. See the comments at
the beginning of startup.S, for more details.
* kern/i386/pc/startup.S (pupa_halt): Modified for the new
compilation mechanism.
(pupa_chainloader_real_boot): Likewise.
(pupa_biosdisk_rw_int13_extensions): Likewise.
(pupa_biosdisk_rw_standard): Likewise.
(pupa_biosdisk_check_int13_extensions): Likewise.
(pupa_biosdisk_get_diskinfo_int13_extensions): Likewise.
(pupa_biosdisk_get_diskinfo_standard): Likewise.
(pupa_get_memsize): Likewise.
(pupa_get_mmap_entry): Likewise.
(pupa_console_putchar): Likewise.
(pupa_console_setcursor): Likewise.
(pupa_getrtsecs): Use pushl instead of push.
* kern/i386/pc/init.c (pupa_machine_init): Use the scratch
memory instead of the stack for a mmap entry, because some
BIOSes may ignore the maximum size and overflow.
* conf/i386-pc.rmk (COMMON_CFLAGS): Added -mrtd and -mregparm=3.
* genmk.rb (PModule#rule): Compile automatically generated
sources with module-specific CFLAGS as well as other sources.
* configure.ac: Check ld.
Replace CFLAGS and CPPFLAGS with BUILD_CFLAGS and BUILD_CPPFLAGS
respectively, before checking endianness and sizes.
* Makefile.in (LD): New variable.
