IRAM/IROM sections.
esp-open-rtos compiled code: .text goes into irom by default, symbols
explicitly marked with IRAM attribute go into iram.
SDK code: .text goes into iram by default, symbols marked with
ICACHE_FLASH_ATTR go into irom.
libgcc functions also go into iram by default.
Closes#7.
It'd be nice to change the linker script so .text is always linked to
IROM instead of needing to objcopy each compiled file. The sticking
point for this is libgcc & libhal, which have symbols in .text that need
to be loaded to IRAM.
* This fixes the problem of axTLS symbols hmac_md5/hmac_sha1 having same
name as symbols in libwpa (which have incompatible signatures)
* Also allows for easier identification and piece-by-piece removal of
binary functions.
* Some libc symbols are not renamed, list is in lib/symbols_norename.txt
