Remove unused hacks for compilers without STL

Patch is ready for review in branch CR24792.

No remarks, please test

There are compilation errors in PRODUCTS:

Linux:
../../../../src/AcisData/AcisData_AcisModel.cxx:304: error: ‘istrstream’ was not declared in this scope
../../../../src/AcisData/AcisData_AcisModel.cxx:304: error: expected ‘;’ before ‘strm’
../../../../src/AcisData/AcisData_AcisModel.cxx:307: error: ‘strm’ was not declared in this scope

WNT:
..\..\..\src\AcisData\AcisData_AcisModel.cxx(304) : error C2065: 'istrstream' : undeclared identifier
..\..\..\src\AcisData\AcisData_AcisModel.cxx(304) : error C2146: syntax error : missing ';' before identifier 'strm'
..\..\..\src\AcisData\AcisData_AcisModel.cxx(304) : error C3861: 'strm': identifier not found
..\..\..\src\AcisData\AcisData_AcisModel.cxx(307) : error C2065: 'strm' : undeclared identifier

..\..\..\src\DxfSat\DxfSat_MakeBody.cxx(69) : error C2664: 'TCollection_HAsciiString::TCollection_HAsciiString(const Standard_CString)' : cannot convert parameter 1 from 'std::basic_string<_Elem,_Traits,_Ax>' to 'const Standard_CString'

Please test branches CR24792 in OCCT and Products repositories.

Dear Commenter 2,

OCCT and Products branch CR24792 was compiled on Linux and Windows platforms and tested.
[revision removed]

Number of compiler warnings:

occt component :
Linux: 21 (21 on master)
Windows: 0 (0 on master)

products component :
Linux: 12 (12 on master)
Windows: 2 (2 on master)

Regressions/Differences:
No regressions/differences

Testing cases:
Not needed

Testing on Linux:
Total MEMORY difference: 351644800 / 352026040
Total CPU difference: 52630.629999999925 / 50789.29000000014

Testing on Windows:
Total MEMORY difference: 380801896 / 381230388
Total CPU difference: 37260.9375 / 36678.890625

There are no differences in images found by testdiff.