Ensure cwrapper compiles without warnings under -std=c99.

Ensure cwrapper compiles without warnings under -std=c99.

* libltdl/config/ltmain.m4sh (func_emit_wrapper_part1):
new function.
(func_emit_wrapper_part2): new function.
(func_emit_wrapper): delegate to new functions.
(func_emit_cwrapperexe_src) [__CYGWIN__ && __STRICT_ANSI__]:
ensure realpath is declared.
(func_emit_cwrapperexe_src): declare two different strings
to each hold part of the wrapper script content. Initialize
using new func_emit_wrapper_partX functions.
(func_emit_cwrapperexe_src) [main]: when emitting wrapper
script content, use both strings.
Reported by Yaakov Selkowitz.