Improve the state of handwritten assembly files (#865)

* Format all handwritten asm and document some

* Use c preprocessor for constants

* Fix

* Fix PI_STATUS_ERROR, some label improvements

* Avoid hi/lo for constants

* Some more comments

* Properly mark functions as functions and their sizes

* Fix merge

* Improvements

* Review suggestions, rework procedure start/end macros to be more like libreultra

* Move IPL3 symbol definitions into ipl3.s

* Fix undefined_syms, add include and language guards to asm.h and fix the comment in gbi.h

* Consistent hex capitalization, add some MIPS builtin defines to CC_CHECK to behave properly

* Add -no-pad-sections assembler option and clean up alignment in gu files and bzero

* Further suggestions and improvements

* Matrix conversion function clarifications

* Fix passing AVOID_UB to gcc

* Suggestions

* Suggestions, global interrupt mask improvements

* Further suggestions, interrupt mask comments

* Comments fixes, rdb.h

* Switch from # comments to // comments, remove unnecesary .set gp=64 directives

* Further review suggestions

* Missed one

include/boot.h

@@ -0,0 +1,6 @@
+#ifndef BOOT_H
+#define BOOT_H
+
+#define BOOT_STACK_SIZE 0x400
+
+#endif