[ASDAlexander77]

TSLANG_ISSUES.md 6: a string returned by C was C's char* itself.

It was worse than stale text:

• a buffer C reuses changed under the program: a = strerror(2); b = strerror(13) printed the second text twice;
• under -mm=rc the reference count lives in the 8 bytes before a string, so retaining C's pointer wrote into memory that isn't the program's. Storing strchr(base, 'k') turned abcdefghijklmnop1 into abddefghijklmnop1, then abedefghijklmnop1; a release reaching zero would free C's pointer.

Change: the result of a call into C, meaning a top-level declare function that nothing in the program defines or a @cpp method (ts.cpp_call), goes through ts.StringCopy. Null stays null, and the copy is owned like any fresh string (markFreshBlockOwned). Declaring the result Opaque gives the raw pointer, for pointer arithmetic or for a string the caller must free. A function in a declare namespace or declare class, as DefaultLib's lib.d.ts declares its methods, is TypeScript and isn't copied.

Merge order: DefaultLib must merge first: ASDAlexander77/TypeScriptCompilerDefaultLib#33. It declares strstr, setlocale, regexp_* and the C time functions Opaque (int for the two that return errno_t). DefaultLib built from older sources with this compiler would break indexOf and RegExp.replace.

Verified:

• test 00c_string_copy.ts fails on alpha100 under gc and rc, and passes under gc, rc, own and none;
• --verify-ownership is silent under rc and own;
• 9M copies in a loop stay flat at ~500 KB private memory under rc and own;
• DefaultLib built with this compiler: gc 163/163, rc 162/163 (1 gc-only skip);
• full Release suite 4080/4080.

Known extra cost: DefaultLib's own TypeScript helpers declared top-level in core.os.d.ts (convertNumber, time_*) are in a separately compiled object, so lib.ts copies their results once more (toFixed, Date strings).

Follow-ups, not in this PR:

• string parameters of @cpp methods that C++ calls (the method has ts.cpp_method): copying needs a release at function exit under rc;
• string fields of C structs can't be told apart from TypeScript tuples.

Docs: docs/c-cpp-header-import.md and docs/cpp-classes.md; TSLANG_ISSUES.md row and section 6.

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