[Linux] Turn off debugging output
Fix an unintended sign extension

Reported by coverity:
>>>     CID 68353:  Unintended sign extension  (SIGN_EXTENSION)
>>>     Suspicious implicit sign extension: "file_header.e_shnum"
with type "unsigned short" (16 bits, unsigned) is promoted in
"file_header.e_shnum * file_header.e_shentsize" to type "int" (32
bits, signed), then sign-extended to type "unsigned long" (64 bits,
unsigned).  If "file_header.e_shnum * file_header.e_shentsize" is
greater than 0x7FFFFFFF, the upper bits of the result will all be 1.
Remove the redundant "/payload" parsing
Compilation fixes for MSVC

It builds and runs with 32-bit, not quite tested yet
Check against NULL before assigning to a string

This fixes https://github.com/zsx/r3/issues/13

Decode_UTF_String returns NULL because the data doesn't have a BOM
Fix encoding detection for READ/string

Files with a BOM are now properly handled. Files without a BOM are again
decoded using UTF-8. Trying to READ/string a file with an encoding for
which support is not yet implemented (UCS4 LE and BE) now causes an
error.

This fixes zsx/r3#13, regressions introduced by 8336a45 and 70c7c3a, and
CureCode issue cc#2186.
Merge pull request #14 from earl/fix-read-string

Fix encoding detection for READ/string
Add a MS visual studio 2010 solution

Note:
 * Only 32-bit version is supported for now.
 * project file for libffi comes from https://github.com/pgregory/libffi-msvc
Do not call OS_Free directly

The core could be built as a library, in which case OS_Free might not
exist.
Fix a typo
Turn off debugging outputs
Move the declaration of As_OS_Str to host-lib.h

To avoid redundence. Ideally, it should be auto-generated, but
make-os-ext only extracts functions starting with "OS_".
Avoid undeclared functions
Scan host-graphics.c for OS_* functions
Declare Crash()
Avoid sign mismatch in comparison
Shutoff compiler warnings with explicit type conversion
Avoid signed integer overflow

"-" on unsigned produces unsigned, and assigning to a signed integer
will cause overflow, which is undefined.
Enable prebuilt.bat
Reduce the executation difference in embedded script

This minimizes the changes needed to embed a script