Font style of instructions in the text is not consistent

[Brian Grayson]

This is based off of the first RC draft of 1.0.0.

In 1.1, slli and slli.uw are in ordinary text font.
In 1.2.5, slli and srai and others are in fixed-width red font (at least in my PDF rendering).
In 1.3's architectural explanation, instructions are in ordinary text font again.
In 1.3.1, orc.b is in bolded ordinary text font.

We should choose one style and use it consistently throughout the document.