[syslinux] elflink: STORAGE_DEVICE_NUMBER proposal

[Gene Cumm]

(I realize this may get delayed)

Per a2fd4f6, the mingw environment should provide a typedef for
STORAGE_DEVICE_NUMBER.  However, several are known to not provide
this.  If it exists, that .definition is preferable to one we may
create.  As a result, a solution should be found for the broken
compilers.

I have a proposal for a solution that while not elegant does achieve this task:

A shell script, gcc-detect-storage_device_number.sh, would use gcc to
attempt to compile a tiny .c module that utilizes
STORAGE_DEVICE_NUMBER, deletes the temporary binary if present and the
script's return value is based on whether the compile is successful.

In win32/Makefile, the return is set to a variable.  If no
STORAGE_DEVICE_NUMBER is defined, do something like "CFLAGS +=
-DSYSLINUX_TYPE_STORAGE_DEVICE_NUMBER=1".

In win32/syslinux.c, change the "#if 0" to "#if
SYSLINUX_TYPE_STORAGE_DEVICE_NUMBER >= 1"

-- 
-Gene