Fix some typos and phrasings.

doc/library/config.txt

@@ -709,19 +709,20 @@ import theano and print the config variable, as in:
 
     Bool value, default: True
 
-    Do NanGuardMode generate an error when it see a nan.
+    Controls whether NanGuardMode generates an error when it sees a nan.
 
 .. attribute:: config.NanGuardMode.inf_is_error
 
     Bool value, default: True
 
-    Do NanGuardMode generate an error when it see an inf.
+    Controls whether NanGuardMode generates an error when it sees an inf.
 
 .. attribute:: config.NanGuardMode.nan_is_error
 
     Bool value, default: True
 
-    Do NanGuardMode generate an error when it see a big value (>1e10).
+    Controls whether NanGuardMode generates an error when it sees a
+    big value (>1e10).
 
 .. attribute:: numpy
 

theano/compile/nanguardmode.py

@@ -132,7 +132,7 @@ class NanGuardMode(Mode):
     ----
         We ignore the linker parameter
     """
-    # We currently loose the 3 first param freuquently, when calling
+    # We currently loose the 3 first params frequently, when calling
     # mode.including() and variant.
     def __init__(self, nan_is_error=None, inf_is_error=None, big_is_error=None,
                  optimizer=None, linker=None):