Gdbinit file and helpers v2

[guillep]

Redo of #475

This pull request adds a .gdbinit file that can be copied at ~/.gdbinit to get common debugging functions and shortcuts for the Pharo VM. The list of all user-defined functions can be accessed in gdb with help user-defined and documentation for a specific function with help function_name.

Printing:

Command	Arguments	Description
ptt	-	Print trampoline table
pf	frame address	Print frame info
pcog	cog method address	Print cog method info
pcogs	-	Print all cogged methods
pct	cog method type	Print all cog methods of a given type
pcp	primitive index	Print all cog methods using a given primitive
pcm	compiled method address	Print all cog methods of a given method
pcs	selector address	Print all cog methods for a given selector

Locating and Disassembling

Command	Arguments	Description
whereis	address	Locates the enclosing cog method or trampoline
dt	trampoline address	Disassemble the given trampoline
dc	cog method address (optional length)	Disassemble the cog method (splits metadata/checks/method body) up to a given length if provided (all method otherwise)
dnc	cog method address (optional length)	Disassemble the cog method (starting at the method body) up to a given length if provided (all method otherwise)

The original merge failed because it was making the build fail (not compile) due the missing printStringOf.

[PalumboN]

🤩

[guillep]

Tests are green!
Thanks @QDucasse !