introduced platform-native thiscall mode (DC_CALL_C_DEFAULT_THIS), as needed for upcoming aggregate support (until now only x86 platforms allowed for specifically selecting thiscall mode, given the different conventions on the same platform); also added respective DC_SIGCHAR_CC_THISCALL ('*')

#!/bin/sh
`which gcc || which clang` -E -P -DGEN_MASM ${1:?Usage: $0 <name> [<outsuffix>]}.S \
	| sed "/^$/d;1i\\
; auto-generated by `basename $0`
;s/$/
/" \
	> $1$2.asm