Support for parsing relocation from objdump (#31)

Basic support for parsing relocation informations as displayed by objdump. It
simply keeps lines that starts by an address, followed by R (instead of
opcodes).
Things like:

      fc:       e8 00 00 00 00  call   101 <gcc_qsort(...*))+0xd7>
           fd: R_X86_64_PLT32      xmalloc-0x4

The only transformations done are replacing tabs between the reloc name (R_XXX)
and the data (anything after the tabs) and prefixing the R_XXX by 4
spaces (matches the behavior of asm-parser.ts).

refs compiler-explorer/compiler-explorer#3222

Signed-off-by: Marc Poulhiès <[email protected]>