Reconstruct template parameters

[ttreyer]

Heavily templated code generates large amount of string to be stored in the .debug_str DWARF section. If the total size is above 4GiB, DWARF cannot address the strings beyond that limit and the linker might refuse to link the program. A solution is to use the compiler option -gsimple-template-names, which remove template parameters from the DW_AT_name of a type, if the full name can be reconstructed by using the template parameter names.

This PR add support for this option to drgn. If a type is templated, but its name doesn't contain the < character, we assume -gsimple-template-names was enabled and we need to reconstruct the full name.

[JakeHillion]

Squashed into facebookexperimental/object-introspection#418 as we don't have a mechanism for PRs on this repo yet (which probably makes sense given that I own it...).