Singular Manual: Version schema for Singular

| ### E.2.1 Version schema for Singular SINGULAR version is of the form `a.b.c.d` which may also be written as `a-b-c-d` where a,b,c and d are numbers: a is changed with major, incompatible changes b is changed with incompatible changes (of some commands/libraries) c is changed with compatible changes (i.e. new commands, extended options, new algorithms, etc.) d is changed with each release (i.e. with bug fixes, etc.) SINGULAR does also have "unofficial" build originating from a code version between "official" version: such builds display "Development version a.b.c" in the header while "official" versions show "version a.b.c". Also the manual describes version a-b-c. To get the complete version number, use `system("version");` or use `SINGULAR_VERSION` in C.

User manual for Singular version 4-1-3p2, 2020, generated by texi2html.