stabs: Implement support for bit fields

[abelbriggs1]

Currently, bit fields are not imported into Ghidra even if they exist in the STABS data.

struct _hierhead { // 0x4
	/* 0x0:0 */ unsigned int opcode : 6;
	/* 0x0:6 */ unsigned int isRelocated : 1;
	/* 0x0:7 */ unsigned int id2 : 11;
	/* 0x2:2 */ unsigned int id1 : 14;
};

This PR implements support for bit fields to be imported.

[chaoticgd]

Looks good. Works fine with all the games I've just tested it on.