added $string= to (ikarus system $strings)
updated announce file
addede case-strings to (vicare syntactic-extensions), review of syntaxes
review of case syntaxes in the syntactic extensions library
reverted definition of library (ikarus system $compiler) in makefile.sps

This definition is probably the cause of issue 39, broken support for
64-bit architectures.  This has been discovered by ChaosEternal (a
Github user).  Reverting this definition should have no consequences
for now.
review of the implementation and use of the macro case-word-size in the boot image code

The old definition of case-word-size from the library (vicare syntactic-extensions)
was making use of the value for "wordsize" form the library (vicare
installation-configuration), which is wrong when building 64-bit boot images
on a 32-bit system.

This fix reimplements case-word-size to use the value of wordsize from the
file "ikarus.config.ss".
removed use of (vicare installation-configuration) from the boot image code
rotated boot image 32-bit
rotated boot image 64-bit