Fix malloc routines to prevent size value wrap-around

Fix malloc routines to prevent size value wrap-around
(Cherry-pick commit f9c8aa3 from 'release-7_6' branch.)

See issue #135 on Github.

* allchblk.c (GC_allochblk, GC_allochblk_nth): Use
OBJ_SZ_TO_BLOCKS_CHECKED instead of OBJ_SZ_TO_BLOCKS.
* malloc.c (GC_alloc_large): Likewise.
* alloc.c (GC_expand_hp_inner): Type of "bytes" local variable changed
from word to size_t; cast ROUNDUP_PAGESIZE argument to size_t; prevent
overflow when computing GC_heapsize+bytes > GC_max_heapsize.
* dbg_mlc.c (GC_debug_malloc, GC_debug_malloc_ignore_off_page,
GC_debug_malloc_atomic_ignore_off_page,
GC_debug_generic_malloc_inner,
GC_debug_generic_malloc_inner_ignore_off_page,
GC_debug_malloc_stubborn, GC_debug_malloc_atomic,
GC_debug_malloc_uncollectable, GC_debug_malloc_atomic_uncollectable):
Use SIZET_SAT_ADD (instead of "+" operator) to add extra bytes to lb
value.
* fnlz_mlc.c (GC_finalized_malloc): Likewise.
* gcj_mlc.c (GC_debug_gcj_malloc): Likewise.
* include/private/gc_priv.h (ROUNDUP_GRANULE_SIZE, ROUNDED_UP_GRANULES,
ADD_SLOP, ROUNDUP_PAGESIZE): Likewise.
* include/private/gcconfig.h (GET_MEM): Likewise.
* mallocx.c (GC_malloc_many, GC_memalign): Likewise.
* os_dep.c (GC_wince_get_mem, GC_win32_get_mem): Likewise.
* typd_mlc.c (GC_malloc_explicitly_typed,
GC_malloc_explicitly_typed_ignore_off_page,
GC_calloc_explicitly_typed): Likewise.
* headers.c (GC_scratch_alloc): Change type of bytes_to_get from word
to size_t (because ROUNDUP_PAGESIZE_IF_MMAP result type changed).
* include/private/gc_priv.h: Include limits.h (unless SIZE_MAX already
defined).
* include/private/gc_priv.h (GC_SIZE_MAX, GC_SQRT_SIZE_MAX): Move from
malloc.c file.
* include/private/gc_priv.h (SIZET_SAT_ADD): New macro (defined before
include gcconfig.h).
* include/private/gc_priv.h (EXTRA_BYTES, GC_page_size): Change type
to size_t.
* os_dep.c (GC_page_size): Likewise.
* include/private/gc_priv.h (ROUNDUP_GRANULE_SIZE, ROUNDED_UP_GRANULES,
ADD_SLOP, ROUNDUP_PAGESIZE): Add comment about the argument.
* include/private/gcconfig.h (GET_MEM): Likewise.
* include/private/gc_priv.h (ROUNDUP_GRANULE_SIZE, ROUNDED_UP_GRANULES,
ADD_SLOP, OBJ_SZ_TO_BLOCKS, ROUNDUP_PAGESIZE,
ROUNDUP_PAGESIZE_IF_MMAP): Rename argument to "lb".
* include/private/gc_priv.h (OBJ_SZ_TO_BLOCKS_CHECKED): New macro.
* include/private/gcconfig.h (GC_win32_get_mem, GC_wince_get_mem,
GC_unix_get_mem): Change argument type from word to int.
* os_dep.c (GC_unix_mmap_get_mem, GC_unix_get_mem,
GC_unix_sbrk_get_mem, GC_wince_get_mem, GC_win32_get_mem): Likewise.
* malloc.c (GC_alloc_large_and_clear): Call OBJ_SZ_TO_BLOCKS only
if no value wrap around is guaranteed.
* malloc.c (GC_generic_malloc): Do not check for lb_rounded < lb case
(because ROUNDED_UP_GRANULES and GRANULES_TO_BYTES guarantees no value
wrap around).
* mallocx.c (GC_generic_malloc_ignore_off_page): Likewise.
* misc.c (GC_init_size_map): Change "i" local variable type from int
to size_t.
* os_dep.c (GC_write_fault_handler, catch_exception_raise): Likewise.
* misc.c (GC_envfile_init): Cast len to size_t when passed to
ROUNDUP_PAGESIZE_IF_MMAP.
* os_dep.c (GC_setpagesize): Cast GC_sysinfo.dwPageSize and
GETPAGESIZE() to size_t (when setting GC_page_size).
* os_dep.c (GC_unix_mmap_get_mem):
Expand ROUNDUP_PAGESIZE macro but without value wrap-around checking
(the argument is of word type).
* os_dep.c (GC_unix_mmap_get_mem): Replace -GC_page_size with
~GC_page_size+1 (because GC_page_size is unsigned); remove redundant
cast to size_t.
* os_dep.c (GC_unix_sbrk_get_mem): Add explicit cast of GC_page_size
to SBRK_ARG_T.
* os_dep.c (GC_wince_get_mem): Change type of res_bytes local variable
to size_t.
* typd_mlc.c: Do not include limits.h.
* typd_mlc.c (GC_SIZE_MAX, GC_SQRT_SIZE_MAX): Remove (as defined in
gc_priv.h now).