[tlbuild] compile fix for luatex

[Vladimir Volovich]

Hi Taco and all!

here is a patch which fixes compilation on solaris 8 sparc using sun
studio compiler:

========================================
--- texk/web2c/web2c/coerce.h	(revision 13085)
+++ texk/web2c/web2c/coerce.h	(working copy)
@@ -22,6 +22,11 @@
 #define	eq_destroy(x)	zeq_destroy(x)
 #endif
 
+#ifdef  synch_p_with_c
+#undef  synch_p_with_c
+#define synch_p_with_c(x) zsynch_p_with_c(x)
+#endif
+
 #else /* luaTeX */
 
 #ifdef	printword
========================================

the error message is:

        cc -DHAVE_CONFIG_H -I. -I../../../texk/web2c -I./.. -I/opt/home/vvv/src/texlive/source/Work/texk -I/opt/home/vvv/src/texlive/source/texk -I/opt/home/vvv/src/texlive/source/Work/libs/zlib -I/opt/home/vvv/src/texlive/source/Work/libs/libpng -DPDF_PARSER_ONLY -I/opt/home/vvv/src/texlive/source/Work/libs/xpdf -I/opt/home/vvv/src/texlive/source/Work/libs/xpdf/goo -I/opt/home/vvv/src/texlive/source/Work/libs/xpdf/xpdf -I/opt/home/vvv/src/texlive/source/Work/libs/obsdcompat -I/opt/home/vvv/src/texlive/source/libs/obsdcompat -I../../../texk/web2c/libmd5 -Iluatexdir -I../../../texk/web2c/luatexdir -I../../../texk/web2c/luatexdir/lua51 -DpdfTeX   -xarch=v8 -O -c -o libluatex_a-vfpacket.o `test -f 'luatexdir/font/vfpacket.c' || echo '../../../texk/web2c/'`luatexdir/font/vfpacket.c
"../../../texk/web2c/luatexdir/font/vfpacket.c", line 184: invalid cast expression
"../../../texk/web2c/luatexdir/font/vfpacket.c", line 194: invalid cast expression
"../../../texk/web2c/luatexdir/font/vfpacket.c", line 220: invalid cast expression
cc: acomp failed for ../../../texk/web2c/luatexdir/font/vfpacket.c

and these lines contain

  pos = synch_p_with_c(cur);

which gets preprocessed to

  pos =  zsynch_p_with_c ( ( scaledpos ) ( cur ) );

and since scaledpos is a structure, it is invalid, because
ISO C forbids casting nonscalar to the same type.

There was a similar fix applied in TL revision 7719 last year.

Best,
v.