Define TRUE/FALSE for plain C/C++ sources via ICU macro

[Copilot]

Building ObjCSword with buildtool fails on its bundled ICU sources (e.g. ucnvbocu.cpp, ucnv_u7.c) with use of undeclared identifier 'FALSE' / 'TRUE'. Newer ICU no longer defines these by default, and plain C/C++ files don't pick them up from GNUstep's Objective-C headers.

Compile flags (XCode/PBXFileReference.m)

• For sourcecode.c.c and sourcecode.cpp.cpp files, -DU_DEFINE_FALSE_AND_TRUE=1 is added to the compile command, so ICU defines TRUE/FALSE itself.
• Objective-C and Objective-C++ files are unchanged.

# before
$CC ... -c dependencies/icu/source/common/ucnv_u7.c ...
# after
$CC ... -c dependencies/icu/source/common/ucnv_u7.c -DU_DEFINE_FALSE_AND_TRUE=1 ...

Review notes

• The flag is ICU-specific. It's harmless to other C/C++ code, but it won't fix the same error from a different library.
• Not built or run against ObjCSword, and no regression test added.

• Fixes Errors while building project with C and C++ code #15