Fix byte sign extensions for architectures with default -funsigned-char

Architectures like armel, armhf, arm64, avr32, powerpc, s390 and s390x use a
unsigned type definition for char. Therefore, the macro for sign extension is
just a nop instruction there. Being more specific on these arches about the
signedness avoids this problem.
Clean up some of the source code formatting.
Fixed a missing semicolon from the last commit.
Removed a redundant if statement condition.

This is already checked in the if-statement before this one.
Remove yet another redundant if-statement check.

Yet again, this is checked in an outer-scope if-statement
- add M64P_MEM_FLAG_*_EMUONLY types to signify memory areas to which the emulated CPU may read or write, but the debugger cannot
- extended read_memory_32() in debugger/dbg_memory.c to be able to read from special memory blocks like RDRAMREG, RSPREG, RSP, DP, VI, AI, etc
- fixed byte order bugs in read_memory_32_unaligned() and write_memory_32_unaligned()
- extended get_memory_flags() in debugger/dbg_memory.c to return new flags and cover special memory spaces
update wiki docs for last commit
Use get_task function instead of passing OSTask_t pointer all over the call hierarchy.
Move alist logic into its own module. Corrected ABI1 and ABI3 sizes.
Extract some helper functions.
Some ucodes report a lower ucode_size than their real size, which causes underdump.

We now overdump by default by using the value 0xf80 used by rspboot ucode.
Extract unknown task/non_task handlers from DoRspCycles.
Reworked rsp execution to improve readability and performances.
Refactoring taskdone.
Use standard memset instead of handcrafted loop.
enforce const correctness no local helper functions. (+ trailing hitespace cleaning)
FORWARD_* constants are uppercase.
Add some comments
Rewrite cicx105_ucode to allow better optimisation. Move it outside of main.

Note: During the rewriting I changed the number of line to write from 0xfc to 0x18 because that's
what I saw in the ipl3 disassembly.
fixed compiler warnings