* Removed unused local vars.

* fix case completeness and unreachable code warnings in compiler that would
be introduced by the next commit

Merge: b9c16b98d1 b08b6a17bd

* reintegrated debug_eh branch
o the LLVM compiler is now functional for Darwin/x86-64, and also (but less
tested) for Linux/x86-64, Linux/AArch64 and Linux/ARMHF. See
https://wiki.freepascal.org/LLVM for details and the current state
o Dwarf-eh-based "zero-cost" exceptions are available with the regular
code generators for Linux/x86-64 and Linux/i386 if the compiler is
compiled with -dpsabieh

* on Mach-O, PECOFF and ELF platforms, write local symbols as hidden/
private_extern (or plain global in case of PECOFF, as the effect is
the same there): visible across object files, but they become local
when linked into a binary/library. This enables cross-unit inlining
of functions accessig implementation-only symbols.

+ introduced TExeSection.MemPosStr - a virtual method for converting the
section's memory position to string for the linker map file. This can be
overriden e.g. for segmented exe formats.

+ x86-64: implemented support for relocation needed by tls threadvars in the binary elf writer

+ support tls threadvars with the internal assembler

+ new relocations for arm tls

+ support for the gnu2 general-dynamic tls model on arm, use it instead of the gnu one as the gnu2 one can be relaxed (access optimizations by the linker)
+ support pic relocations in the internal assembler writer

+ dwarf support for tls threadvars

+ support for arm attributes
* abi notes fixed

* change TObjData.sectiontype2options to a class function so that it can be called without an instance of TObjData

+ add a method to TObjData to retrieve the TSectionProcBits and TSectionFlags values for a given section type

* parameters declared as out must be initialized

* fixed default value for progbits

* use translateable error messages for undefined symbols and also report in which object file the symbol was first found

+ implement relocations for Aarch64 for the internal COFF linker

* it's rather useless that sectiontype2options is virtual as we can't use a class type, not to mention that the classes doing the overriding are for the internal assemblers/linkers, but we need it also for external
Thus we move the functionality of the overloads to the basemethod and remove the virtual directive; maybe we'll find a better solution in the future...

+ lots of fixes to the Z80 internal asm writer

+ call ApplyAsmSymbolRestrictions for symbols that should be exported from ar files

* fixed the TRelocDataInt to avoid truncating 16-bit addresses to 8-bit on 8-bit CPUs

* the len parameter of TObjData.alloc changed to TObjSectionOfs

* ImageBase changed to qword (same type as CurrMemPos) to avoid truncating to 8-bit on Z80

* the len parameter of TObjData.writebytes changed to TObjSectionOfs to avoid 8-bit truncation on Z80

* Added virtual function TObjSection.GetAltName to be able to specify additional section name by descendants.
* OMF: Use the name of the first global symbol as an addition section name. This name is visible in the linker map file and helps tracking of section references.

* fix for Mantis 0037559: the adjustment of the section type should only be done for internal COFF writers

* correctly handle PE COMDAT sections: like for the Comdat groups in ELF files the unused symbols need to be converted to externals so that relocations are handled correctly