bugfix src_files naming

[rtl] Add 16 external performance counters at mhpmcounter[28:13]

[rtl] Add CLINTx: 32 fast interrupts and custom CSRs + ACK signaling

This commit adds 32 non-standard, custom, fast interrupts to Ibex. These
interrupts are managed via 3 custom CSRs: `miex`, `mipx` and `mtvecx`.
`mtvecx` is initialized just like `mtvec`. Upon handling such a custom
interrupt, the core uses two signals (ACK + ID) to inform a possible
platform-level interrupt controller accordingly.

The purpose of adding these non-standard interrupts is to have an
interrupt framework compatible with RI5CY/CV32E40P for platforms that can
use the two cores interchangeably (PULP/PULPissmio).

Signed-off-by: Pirmin Vogel <vogelpi@lowrisc.org>

Tracing: Wrap fatal error message with `$fatal()`

The syntax of this statement is not correct without the `$fatal()` SV
construct. This causes errors in some tools even if the error condition
is not met.

FIXED:

step on a jal instruction (from Olivier Montfort)
ra register not update when single step debug #3

Removed non-ASCII characters

update headers

fixed fetch fifo [broken after last commit]