Add support for writing relocations. Since the symbol numbering is only
available after the symbols are written, the relocations are collected
in a vector. At write time, the relocations are converted using the
symbols ids, compressed and written out. A relocation data record is
limited to 32K-1 bytes, which requires making sure that larger
relocation data is written into multiple records.
Sections which are not allowed to carry data are marked as virtual. Only
complication when writing out the text is that it must be written in
chunks of 32k-1 bytes, which is done by having a wrapper stream writing
those records.
Data of BSS sections is not written, since the contents is known to be
zero. Instead, the fill byte value is used.
Unlike other formats, the GOFF object file format uses a 2 dimensional structure
to define the location of data. For example, the equivalent of the ELF .text
section is made up of a Section Definition (SD) and a class (Element Definition;
ED). The name of the SD symbol depends on the application, while the class has
the predefined name C_CODE/C_CODE64 in AMODE31 and AMODE64 respectively.
Data can be placed into this structure in 2 ways. First, the data (in a text
record) can be associated with an ED symbol. To refer to data, a Label
Definition (LD) is used to give an offset into the data a name. When binding,
the whole data is pulled into the resulting executable, and the addresses
given by the LD symbols are resolved.
The alternative is to use a Part Definition (PR). In this case, the data (in
a text record) is associated with the part. When binding, only the data of
referenced PRs is pulled into the resulting binary.
Both approaches are used. SD, ED, and PR elements are modeled by nested
MCSectionGOFF instances, while LD elements are associated with MCSymbolGOFF
instances.
At the binary level, a record called "External Symbol Definition" (ESD) is used. The
ESD has a type (SD, ED, PR, LD), and depending on the type a different subset of
the fields is used.
