1. separate rom include files and linkscript to esp_rom
2. modefiy "include rom/xxx.h" to "include esp32/rom/xxx.h"
3. Forward compatible
4. update mqtt
In some cases, linker could choose to use ROM functions instead of the
ones defined in IDF.
For functions used in ROM stub table, this would lead to infinite
recursion when the corresponding function was called from ROM.
For crypto functions, some of these were modified in IDF, and
incompatible with ROM counterparts.
- add two versions of libc: libc.a and libc_nano.a. First one has full C99 formatting support, second one uses “nano” formatting functions available in ROM.
- fix linker error for fmod, fmodf, atof, atoff
- update tests
- spaces->tabs in tasks.c
- update vfs_uart.c to use per-UART locks
- add license to vfs_uart.c
- allocate separate streams for stdout, stdin, stderr, so that they can be independently reassigned
- fix build system test failure
